a guide to programming in java critical thinking answers

Java Arrays
Java Strings
Java Collection
Java 8 Tutorial
Java Multithreading
Java Exception Handling
Java Programs
Java Project
Java Collections Interview
Java Interview Questions
Spring Boot
Java Exercises - Basic to Advanced Java Practice Set with Solutions

1. Write Hello World Program in Java

2. write a program in java to add two numbers., 3. write a program to swap two numbers, 4. write a java program to convert integer numbers and binary numbers..

5. Write a Program to Find Factorial of a Number in Java
6. Write a Java Program to Add two Complex Numbers

7. Write a Program to Calculate Simple Interest in Java

8. Write a Program to Print the Pascal’s Triangle in Java

9. Write a Program to Find Sum of Fibonacci Series Number

10. write a program to print pyramid number pattern in java., 11. write a java program to print pattern., 12. write a java program to print pattern., 13. java program to print patterns., 14. write a java program to compute the sum of array elements., 15. write a java program to find the largest element in array, 16. write java program to find the tranpose of matrix, 17. java array program for array rotation, 18. java array program to remove duplicate elements from an array, 19. java array program to remove all occurrences of an element in an array, 20. java program to check whether a string is a palindrome, 21. java string program to check anagram, 22. java string program to reverse a string, 23. java string program to remove leading zeros, 24. write a java program for linear search., 25. write a binary search program in java., 26. java program for bubble sort..

27. Write a Program for Insertion Sort in Java

28. Java Program for Selection Sort.

29. java program for merge sort., 30. java program for quicksort., java exercises – basic to advanced java practice programs with solutions.

Looking for Java exercises to test your Java skills, then explore our topic-wise Java practice exercises? Here you will get 25 plus practice problems that help to upscale your Java skills.

As we know Java is one of the most popular languages because of its robust and secure nature. But, programmers often find it difficult to find a platform for Java Practice Online. In this article, we have provided Java Practice Programs. That covers various Java Core Topics that can help users with Java Practice.

So, with ado further take a look at our free Java Exercises to practice and develop your Java programming skills. Our Java programming exercises Practice Questions from all the major topics like loops, object-oriented programming, exception handling, and many more.

Topic Wise Java Exercises List

Pattern Programs in Java
Array Programs in Java
String Programs in Java

Java Practice Problems for Searching Algorithms

Practice problems in java sorting algorithms, more java practice exercises.

Java Practice Programs

This Java exercise is designed to deepen your understanding and refine your Java coding skills, these programs offer hands-on experience in solving real-world problems, reinforcing key concepts, and mastering Java programming fundamentals. Whether you’re a beginner who looking to build a solid foundation or a professional developer aiming to sharpen your expertise, our Java practice programs provide an invaluable opportunity to sharpen your craft and excel in Java programming language .

The solution to the Problem is mentioned below:

Click Here for the Solution

5. write a program to find factorial of a number in java., 6. write a java program to add two complex numbers., 8. write a program to print the pascal’s triangle in java, java exercise on pattern.

Array Exercises in Java

String Exercises in Java

Time Complexity: O(N) Space Complexity: O(N)

Time Complexity: O(logN) Space Complexity: O(N)

Time Complexity: O(N 2 ) Space Complexity: O(1)

27. Write a Program for Insertion Sort in Java.

Time Complexity: O(N logN) Space Complexity: O(N)

Time Complexity: O(N logN) Space Complexity: O(1)

After completing these Java exercises you are a step closer to becoming an advanced Java programmer. We hope these exercises have helped you understand Java better and you can solve beginner to advanced-level questions on Java programming.

Solving these Java programming exercise questions will not only help you master theory concepts but also grasp their practical applications, which is very useful in job interviews.

Java Array Exercise Java String Exercise Java Collection Exercise Click Here – To Practice Java Online please check our Practice Portal.

Java Exercise – FAQ

1. how to do java projects for beginners.

To do Java projects you need to know the fundamentals of Java programming. Then you need to select the desired Java project you want to work on. Plan and execute the code to finish the project. Some beginner-level Java projects include: Reversing a String Number Guessing Game Creating a Calculator Simple Banking Application Basic Android Application

2. Is Java easy for beginners?

As a programming language, Java is considered moderately easy to learn. It is unique from other languages due to its lengthy syntax. As a beginner, you can learn beginner to advanced Java in 6 to 18 months.

3. Why Java is used?

Java provides many advantages and uses, some of which are: Platform-independent Robust and secure Object-oriented Popular & in-demand Vast ecosystem

Please Login to comment...

Improve your Coding Skills with Practice

What kind of Experience do you want to share?

110+ Java Interview Programs With Solutions

May 16, 2023
Java Interview Programs

41 Comments

Quick reference sheets :.

In this post, I have listed some of the most popular Java interview programs with link to their solutions. I hope these programs will be helpful for you guys to prepare for technical interview.

1) How to reverse a string in Java?

Any technical interview is not complete without a question on recursive concept. This question is one of them. You have to write a Java program to reverse a given string using recursive method. [ Solution ]

2) How to create a pyramid of numbers in Java?

This is one of the Java logical programs asked in interview. Write a Java program to create a pyramid of numbers or any other symbols in pyramid patterns. [ Solution ]

3) How do you remove all white spaces from a string in Java?

The bundle of Java programming interview questions is incomplete without the questions on strings. You will face many questions on string handling in your interview. I have listed some of them in this post. It is one of them. [ Solution ]

4) How to find duplicate characters in a string in Java?

Write a Java program to find duplicate characters and their count in a given string. For example, in a string “Better Butter” , duplicate characters and their count is t : 4, e : 3, r : 2 and B : 2. [ Solution ]

5) How do you check the equality of two arrays in Java?

One more favorite topic of many interviewers is array. You will face many Java coding interview questions related to array. In this program, you will learn how to check the equality of two arrays using different methods. [ Solution ]

6) Anagram program in Java

Write a Java program to check whether two given strings are anagram or not. Two strings are said to be anagram if they contain same set of characters but in different order. For example, “Mother In Law” and “Hitler Woman” are anagrams. This type of Java programming questions test the coding skills of a candidate. [ Solution ]

7) Armstrong number program in Java

Write a Java program to check whether a given number is Armstrong number or not. A number is called an Armstrong number if it is equal to sum of its digits each raised to the power of number of digits in it. For example: 153 , 9474 , 54748 are some Armstrong numbers. In Java interview coding questions like this, an interviewer mainly check how do you implement logic in you code. [ Solution ]

8) How to find duplicate elements in an array?

I think array related programs along with string handling programs are the most asked Java programs in interview. In this program, I have discussed five methods to find duplicate elements in the given array. [ Solution ]

9) How to find sum of all digits of a number in Java?

Write a Java program to find sum of all digits of a given number. [ Solution ]

10) How to find second largest number in an integer array?

Write a Java program to find second largest number in an array of numbers. [ Solution ]

11) How to perform matrix operations in Java?

Write a Java program to perform matrix operations like matrix addition, matrix subtraction, matrix multiplication and transpose of a matrix. This program is one of the matrix related Java programs asked in interview. [ Solution ]

12) How to count occurrences of each character in a string in Java?

Write a Java program to count the number of occurrences of each character in a given string. For example, If “Java J2EE Java JSP J2EE” is the given string then occurrences of each character in this string is E=4, 2=2, v=2, =4, P=1, S=1, a=4, J=5 . [ Solution ]

13) How to find largest number less than a given number and without a given digit?

Write a Java program to find the largest number ‘L’ less than a given number ‘N’ which should not contain a given digit ‘D’ . For example, If 145 is the given number and 4 is the given digit, then you should find the largest number less than 145 such that it should not contain 4 in it. In this case, 139 will be the answer. This program is one of the logical programs in Java. [ Solution ]

14) How to find all pairs of elements in an array whose sum is equal to given number?

Write a Java program to find all pairs of elements in the given array whose sum is equal to a given number. For example, if {4, 5, 7, 11, 9, 13, 8, 12} is an array and 20 is the given number, then you have to find all pairs of elements in this array whose sum must be 20 . In this example, (9, 11) , (7, 13) and (8, 12) are such pairs whose sum is 20 . [ Solution ]

15) How to find continuous sub array whose sum is equal to given number?

Write a Java program to find continuous sub array of the given array whose sum is equal to a given number. For example, If {12, 5, 31, 9, 21, 8} is the given array and 45 is the given number, then you have to find continuous sub array in this array such that whose elements add up to 45 . In this case, {5, 31, 9} is such sub array whose elements add up to 45 . [ Solution ]

16) How to remove duplicate elements from ArrayList in Java?

Write a Java program to remove duplicate elements from already constructed ArrayList. This program is one of the collection interview programs in Java. [ Solution ]

17) How to check whether given number is binary or not?

Write a Java program to check whether given number is binary or not. A binary number is a number which contains only 0 or 1 . For example : 101101, 110010110, 10010011 are binary numbers. This program is one of the number related basic Java programs for interview. [ Solution ]

18) How to check whether one string is a rotation of another in Java?

Write a Java program to check whether one string is a rotation of another. For example, If “JavaJ2eeStrutsHibernate” is a string then some rotated versions of this string are “StrutsHibernateJavaJ2ee” , “ J2eeStrutsHibernateJava “, “ HibernateJavaJ2eeStruts “. [ Solution ]

19) How to find intersection of two arrays in Java?

Write a Java program to find intersection of two arrays or common elements between the two arrays. [ Solution ]

20) How to check whether user input is number or not in Java?

Write a Java program to check whether user has entered a number or not. [ Solution ]

21) How to find trigonometric values of an angle in Java?

Write a Java program to find trigonometric values like sin, cos, tan, sec, cosec and cot of an angle. This program is one of the mathematics related Java practice programs. [ Solution ]

22) How to reverse each word of a string in Java?

Write a Java program to reverse each word of a given string. For example, If “Java Concept Of The Day” is input string then output should be “avaJ tpecnoC fO ehT yaD”. [ Solution ]

23) How to separate zeros from non-zeros in an array?

Write a Java program to separate zeros from non-zeros in the given array. You have to move zeros either to end of the array or bring them to beginning of the array. For example, if {14, 0, 5, 2, 0, 3, 0} is the given array, then moving zeros to end of the array will result {14, 5, 2, 3, 0, 0, 0} and bringing zeros to front will result {0, 0, 0, 14, 5, 2, 3}. [ Solution ]

24) Decimal To Binary, Decimal To Octal And Decimal To HexaDecimal In Java

Write a Java program to convert decimal to binary, decimal to octal and decimal to hexadecimal. Number conversion programs are very common Java interview programming questions for freshers. [ Solution ]

25) How to find all the leaders in an integer array in Java?

Write a Java program to find all the leaders in an integer array. An element is said to be a leader if all the elements on it’s right side are smaller than it. Rightmost element is always a leader. For example, if {14, 9, 11, 7, 8, 5, 3} is the given array then {14, 11, 8, 5, 3} are the leaders in this array. [ Solution ]

26) Reverse and add until you get a palindrome

Write a Java program to take input number from the user, reverse it and add it to itself. If the sum is not a palindrome then repeat the procedure until you get a palindrome. [ Solution ]

27) Selection sort in Java

Write a Java program to implement selection sort. [ Solution ]

28) Reverse the string with preserving the position of spaces

Write a Java program to reverse a string with preserving the position of spaces. For example, if “I Am Not String” is the given string then the reverse of this string with preserving the position of spaces is “g ni rtS toNmAI” . [ Solution ]

29) Roman equivalent of a decimal number

Write a Java program to find roman equivalent of a decimal number. [ Solution ]

30) percentage of uppercase, lowercase, digits and special characters in a string

Write a Java program to find the percentage of uppercase letters, lowercase letters, digits and other special characters(including space) in the given string. [ Solution ]

31) Launch external applications through Java code

Write a Java program to launch external applications like notepad, MS Word etc. [ Solution ]

32) Find missing number in an array

If ‘ n ‘ is the positive number and ‘ a ‘ is an array of integers of length ‘n-1’ containing elements from 1 to n. Then find the missing number in ‘a’ in the range from 1 to n. Occurrence of each element is only once. For example, If n = 8, then array ‘a’ will have 7 elements in the range from 1 to 8. For example {1, 4, 5, 3, 7, 8, 6}. One number will be missing in ‘a’ (2 in this case). You have to find out that missing number. [ Solution ]

33) String immutable program

Write a Java program to prove strings are immutable in java. [ Solution ]

34) Arrays.deepToString() method example. [ Solution ]

35) 18 Java ArrayList Programming Examples.

These programs are collections related Java coding questions. [ Solution ]

36) 16 Java LinkedList Programming Examples.

37) Detection of deadlocked threads

Write a Java program to detect the deadlocked threads. [ Solution ]

38) Generate random numbers

Write a Java program to generate random numbers. [ Solution ]

39) Java PriorityQueue Example. [ Solution ]

40) Java HashSet Example. [ Solution ]

41) Java LinkedHashSet Example. [ Solution ]

42) Java TreeSet Example. [ Solution ]

43) How to sort a text file in Java?

Write a Java program or function to sort a text file containing some records in single or multiple columns. Your program should take one text file containing some records as input, should sort the records on a particular column and write the sorted records in another text file. [ Solution ]

44) Array to ArrayList and ArrayList To Array Conversion program. [ Solution ]

45) How do you find longest substring without repeating characters in a string?

Write a Java program or function to find the longest substring without repeating characters in a given string. For example, if “javaconceptoftheday” is the input string, then the longest substring without repeating or duplicate characters is “oftheday” . [ Solution ]

46) How do you count occurrences of each element in an array?

Write a Java program or function to count the occurrences of each element in an array. For example, if {12, 9, 12, 9, 10, 9, 10, 11} is the input array, then the count of occurrences of each element is {12:2, 9:3, 10:2, 11:1} . [ Solution ]

47) Reverse an array.

Write a Java program to reverse an array without using an additional array. That means your program should reverse the given array in place. For example, if {12, 9, 21, 17, 33, 7} is the input array, then your program should return {7, 33, 17, 21, 9, 12} as output. [ Solution ]

48) Write a Java program to swap two string variables without using third or temp variable? [ Solution ]

49) Finding the most repeated word in a text file.

Write a Java program to find the most repeated word in text file. Your program should take one text file as input and find out the most repeated word in that file. [ Solution ]

50) How do you stop a thread in Java? [ Solution ]

51) Remove duplicate elements from an array.

Write a Java program to remove duplicate elements from the given array. Your program or method should take an array of integers as input and should return another array which should contain only unique elements from the input array. For example, if {4, 3, 2, 4, 9, 2} is the input array then your program or method should return {4, 3, 2, 9} as output. [ Solution ]

52) Write a Java program to append text to a file? [ Solution ]

53) How do you synchronize ArrayList, HashSet and HashMap in Java? [ Solution ]

54) Write a Java program to find number of characters, number of words and number of lines in a text file? [ Solution ]

55) How do you convert HashMap to ArrayList in Java? [ Solution ]

56) Write a Java program to sort an ArrayList? [ Solution ]

57) All permutations of a string.

Write a Java program to find all permutations of a string recursively. For example, all permutations of string “ JSP “ are,

JSP JPS SJP SPJ PJS PSJ

[ Solution ]

58) Check number belongs to Fibonacci series or not.

Write a Java program to check whether given number belongs to Fibonacci series or not. For example, 34 belongs to Fibonacci series where as 51 doesn’t belongs to Fibonacci series. [ Solution ]

59) 15 Java HashMap programming examples. [ Solution ]

60) Write a Java program to print Floyd’s Triangle? [ Solution ]

61) Finding The First Repeated And Non-Repeated Character In A String.

Given a string, your code must find out the first repeated as well as non-repeated character in that string. For example, if “ JavaConceptOfTheDay ” is the given string, then ‘J’ is a first non-repeated character and ‘a’ is a first repeated character. [ Solution ]

62) Spiral Matrix Program.

Write a Java program to create spiral of numbers or spiral matrix or circular matrix of order n*n in both clockwise and anti-clockwise directions. Spiral matrix should be filled with the values from 1 to n*n. [ Solution ]

63) String to Integer and Integer to String Conversion program. [ Solution ]

64) Array Element Removal Programs.

These Java interview programs contain,

–>How to remove an element at specific index from an array?

–>How to remove specific element from an array?

–>How to remove multiple elements at different indices from an array?

–>How to remove multiple specific elements from an array?

–>How to remove all occurrences of an element in an array?

These programs have been demonstrated using third party library org.apache.commons.lang3.ArrayUtils class. [ Solutions ]

65) How to find type, total space, free space and usable space of all drives in Java?

This is also one of Java coding interview question related to type and space of drives of a computer. In this post, you will learn how to list all drives of a computer, how to find type of a drive and how to find total space, free space and usable space of all drives using Java code. [ Solution ]

66) Palindrome Programs In Java

Palindrome programs are one of the most asked Java programming interview questions for freshers. In this article, you will learn to write palindrome program using 4 different methods. They are iterative method, recursive method, Palindrome program using StringBuffer and palindrome program using IntStream of Java 8. [ Solution ]

67) Array Rotation Program In Java

Array rotation means you need to rotate an array in left or right direction by ‘n’ positions. For example, if {1, 2, 3, 4, 5, 6, 7} is an input array then rotating this array in the left direction by two positions will give {3, 4, 5, 6, 7, 1, 2} and rotating in the right direction by two positions will give {6, 7, 1, 2, 3, 4, 5} . [ Solution ]

68) Prime Number Programs In Java

Prime number programs are one of the popular and regular Java programs asked in interview. In this post, you will find following prime number programs.

->How to check whether given number is prime or not?

->How to find initial 10 or 20 or 30 …… n prime numbers?

->How to find out 20 (or 30 or 40 …… n ) prime numbers after 100 ( or after any given number)?

->How to find out all prime numbers between two given numbers?

->How to find the sum of initial ‘ n ‘ prime numbers?

->How to find sum of all prime numbers between two given numbers?

->How to print prime numbers between two given numbers in the reverse order?

->How to find the twin prime numbers?

->How to print twin prime numbers between two given numbers?

->How to find a prime number which comes after three non-prime numbers?

[ Solutions ]

69) How to make collection read-only in Java?

In this article, you will learn how to make collection read-only in Java using unmodifiable wrapper methods of java.util.Collections. [ Solution ]

70) How to reverse a sentence word by word in Java?

Write a Java program to reverse a sentence word by word? For example, If “Java Concept Of The Day” is an input string then output will be “Day The Of Concept Java”. This type of Java interview coding questions are asked by the interviewer to test the coding skills of a candidate. [ Solution ]

71) How to make text file read-only in Java?

In this post, you will see 3 Java programs asked in interview related to file handling. They are – how to make text file read-only, how to check whether existing text file read-only or not and how to make read-only file writable again in Java. [ Solutions ]

72) How to remove all vowels from a string in Java?

Write a Java program to remove all vowels from a string. Your program should take input string from the user and remove all vowels from this string and print it without vowels. This type of Java coding questions are very popular in interview for freshers. [ Solution ]

73) How to copy a text file in Java?

Write a Java program to copy the contents of one text file to another text file. Your program should take two text files as input and copy the contents of source file to destination file. In this post, you will learn to copy a text file using I/O Stream , using Files.copy() method and using FileChannel class. This program is one of Java interview programming questions related to file handling. [ Solution ]

74) How to find the most frequent element in an array in Java?

Write a Java program to find the most frequent element in an array. In this article, you will learn to find the most frequent element and its frequency in an array of integers using HashMap . This type of Java logical programs related to array or strings are very common in interview for freshers. [ Solution ]

75) Text File Modification Program

How to modify a text file or How to replace specific string in a text file? It is one of the basic Java programs for interview related to I/O programming or file handling programming. [ Solution ]

76) Harshad Number (Niven Number) Program

Harshad number or niven number is a number which is divisible by the sum of its digits. For example, 21 is a Harshad number because 21 is divisible by the sum of its digits (2+1=3). An interviewer ask this type of logical programs in interview to test how do you implement logic in your code. [ Solution ]

77) How to find saddle point of a matrix in Java?

Saddle point of a matrix is an element in the matrix which is smallest in its row and largest in its column. For example,

6 3 1 9 7 8 2 4 5

In this matrix, 7 is the saddle point. Because it is the smallest in its row (2 nd row) and largest in its column (2 nd column). [ Solution ]

78) How to find union and intersection of multiple arrays in Java?

You have seen union and intersection of two arrays. In this post, you will see union and intersection of multiple arrays. [ Solution ]

79) How to read and write images in Java?

An interviewer ask this type of Java interview programs to test basic file handling skills or I/O programming skills of a candidate. [ Solution ]

80) How to compare two text files in Java?

Your program should take two text files as input and compare their content line by line and find out whether they have same content or not. [ Solution ]

81) Difference between two dates in Java

Your program should take start date and end date from the user and find out the difference between these two dates in terms of years, days, hours, minutes and seconds. This is one of the commonly asked Java programming interview questions for freshers. [ Solution ]

82) How to find frequency of all digits in a number in Java?

Your program should take one number from the user and find out frequency of all digits in this number. This program is one of the core Java coding interview questions for freshers. [ Solution ]

83) Symmetric Matrix Program In Java

Symmetric matrix is a square matrix which is equal to its transpose. If A[][] is a square matrix with (M x M) order, then this matrix is said to be symmetric if every element at i th row and j th column is equal to element at j th row and i th column i.e A[i][j] == A[j][i]. Your program should take input matrix from the user, display it and check whether the matrix is symmetric or not. As I said earlier, an interviewer ask this type of Java programs in interview to check how do you implement logic in your code. [ Solution ]

84) How to set file permissions in Java?

In this program, you will learn to set different file permissions like read, write and execute using different methods of java.io.File class . [ Solution ]

85) How to list all files in a directory in Java?

This program is one of the file handling Java programs likely to be asked in interview. [ Solution ]

86) How to format date in Java?

In this program, you will learn how to format date using SimpleDateFormat class. [ Solution ]

87) Pattern Programs In Java

Java programs to print numbers or characters or any other symbols in different shapes or patterns are one of the frequently asked Java interview coding questions for freshers. Because, they test the logical ability as well as coding skills of a candidate. In this post, I have collected some different pattern programs asked in interview. I hope they will be helpful for you guys to prepare for interview. [ Solution ]

88) How to reverse an ArrayList in Java? [ Solution ]

89) Diamond Pattern Programs In Java. [ Solution ]

90) How to zip files in Java? [ Solution ]

91) How to unzip files in Java? [ Solution ]

92) Magic number program in Java

Write a Java program which checks whether given number is a magic number or not. Magic number is a number which gives sum exactly 1 when its digits are recursively added. [ Solution ]

93) Array Triplets Java Program-1

Write a Java program to find array triplets such that sum of first two elements equals the third element. [ Solution ]

94) Array Triplets Java Program-2

Write a Java program which finds triplets in the given array whose sum is equal to given number. [ Solution ]

95) How to sort an array of 0s and 1s? [ Solution ]

96) How to sort an array of 0s, 1s and 2s? [ Solution ]

97) Contiguous sub arrays with given sum

Write a Java program which prints all contiguous sub arrays with given sum. For example, if [5, -9, 4, -2, 7, 1, -4, -3, -7] is the given array and -7 is the given sum then contiguous sub arrays with sum -7 are [-9, 4, -2], [-4, -3] and [-7]. [ Solution ]

98) Contiguous sub array with maximum sum

Write a Java program which takes an integer array as input and prints contiguous sub array with maximum sum. For example, if {2, -3, 7, -4, 2, 5, -8, 6, -1} is the given array then contiguous sub array with maximum sum is {7, -4, 2, 5} and its sum is 10. [ Solution ]

99) Java program to find smallest and second smallest element in an integer array. [ Solution ]

100) Disarium Number Program In Java

Write a Java program which checks whether given number is Disarium number or not. A number is said to be Disarium if it is equal to sum of its digits raised to the power of their respective position in the number. [ Solution ]

101) Java program to print all sub strings of a string. [ Solution ]

102) How to sort HashMap by keys in Java 8? [ Solution ]

103) How to sort HashMap by values in Java 8? [ Solution ]

104) How to merge two maps with same keys in Java 8? [ Solution ]

105) How to merge two sorted arrays in Java? [ Solution ]

106) How to merge two unsorted arrays in sorted order in Java? [ Solution ]

107) How to merge two sorted or unsorted arrays into single sorted array without duplicates in Java? [ Solution ]

108) How to sort array elements by frequency in Java? [ Solution ]

109) Java program to find common elements in all rows of a matrix. [ Solution ]

110) Java program to print common characters between two strings in alphabetical order . [ Solution ]

111) Most repetitive character in a string

Write a Java program to find most repetitive character or maximum occurring character in the given string. For example, if “Java Concept Of The Day” is the input string then ‘a’ is the maximum occurring character which occurred 3 times in the string. [ Solution ]

112) Minimum absolute difference program

You are given an unsorted array of integers, write a Java program to find the minimum absolute difference between any two elements of the given array. [ Solution ]

113) Pronic number program in Java

Write a Java program to check whether the given number is pronic or not. Pronic number is a number which is the product of two consecutive integers i.e n(n+1). [ Solution ]

114) Odd and even numbers by two threads in Java

Write a Java program where two threads print odd and even numbers in sync. That means, one thread should print only the odd numbers and another thread should print only the even numbers. But, both threads should communicate with each other so that numbers should be printed in natural order. [ Solution ]

115) Bubble Sort Algorithm In Java [ Solution ]

Keep checking this page for more Java interview programs and Java programming coding interview questions.

Click to share on Twitter (Opens in new window)
Click to share on Facebook (Opens in new window)
Click to share on LinkedIn (Opens in new window)
Click to share on Reddit (Opens in new window)
Click to share on Pinterest (Opens in new window)
Click to share on WhatsApp (Opens in new window)
Click to email a link to a friend (Opens in new window)
Click to share on Tumblr (Opens in new window)
Click to share on Pocket (Opens in new window)
Click to share on Telegram (Opens in new window)

80+ pattern programs in java.

November 22, 2023
571 Comments

Magic Number Program In Java

February 24, 2021

How To Find Array Triplets With Sum Of Two Elements Equals Third?

October 28, 2020

Great work.

Very useful blog.

Nice blog ever seen..Good work.!!

This is great work.The best for any one wants to learn java. Thank you for all the efforts you put in to develop such awesome blog for us

Thank you sir,very useful java programs

This is super material!!!!!!!

The java.io package explanation is missing here in this site, hope you will update it soon 😉

and i want to contribute a little here, one question related to serialization which may be asked in interviews.

can we make a subclass as non-serializable while the super class is implementing Serializable interface.?

Class A implements Serializable{ } class B extends A{ }

How to prevent class B to serialize here.?

hope to hear you soon.. 😉

There is no direct way to prevent subclass from serialization in java. One possible way by which a programmer can achieve this is by implementing the writeObject() and readObject() methods in the subclass and needs to throw NotSerializableException from these methods. These methods are executed during serialization and de-serialization respectively. By overriding these methods, we are just implementing our own custom serialization.

Really impressive for your work!!! It is a good site to learn the java for everyone. Thank you very much for your efforts.

Very much beneficial stuff here. Great work. Thumbs up.

Highly Required Information. Good Job…

It is a good site to learn the java for everyone. Thank you very much for your efforts. Thank you;

Loved It !!!!!!!!!

Super it for … who want scarch level knowledge on java

important questions asked in interviews great work

Its Awesome!….. But i need more interview questions with answers to improve our knowledge>>

very precious blog. very good job. keep it up. so many thank you.

How to print the following pattern using Java Program?

* *** ABCDEF *** *

class Star { public static void main(String[]args) { System.out.println(“*”); System.out.println(“**”); System.out.println(“ABCDEF”); System.out.println(“**”); System.out.println(“*”); } }

public class demoTest {

public static void main(String[] args) { for (int i = 1; i <= 2; i++) { for (int j = 1; j <= i; j++) { System.out.print("*"); } System.out.println(); } for (int i = 'A'; i <= 'F'; i++) { System.out.printf("%c", i); } System.out.println();

for (int k = 1; k = k; j–) { System.out.print(“*”); } System.out.println(); }

Very helpful.Thanks a lot.

Thanks for the information sir,nice one sir i serached the programs in the google but i didnot got easy solution to solve the problem ..This website is awesome sir and suggest one more website to learn J2EE and HIBERNATE

Print the pattern in java 1 2 4 3 6 9 4 8 12 16

public class MainClass { public static void main(String[] args) { // TODO Auto-generated method stub for(int i=1;i<=4;i++) { int cnt=1; for(int j=1;j<=i;j++) { System.out.print(" "+i*cnt); cnt++; } System.out.println(); } } }

public class numberpattern { public static void main(String[] args) { int i,j; for(i=1;i<=4;i++) { int count=1; for(j=1; j<=i; j++) { System.out.print(" "+i*j);

} System.out.println(" " );

Amazing Work Sir…Its really very Helpfull

very helpful thank u

Good job. Very much helpful. keep going pls

} System.out.println(" ");

very useful for every java developer

Sir your website is very very usefull for the beginners to understand the the basics. loved it..

Nice work ,this gives a good help to learning the concept and logic of java programming

good programs in easy and understandable manner

sir some questions are missing like,

if String input=”aabbbccdddd”; o/p=step1-abbbccdddd 2-abccdddd 3-abcdddd 4-abcd

if o/p is empty string then print “” how it will (mine last interview questions)

2nd q-> i/p=>{1,7,5,9,0,1,5,2,1,8,0} o/p=>{0,0,1,1,1,2,5,5,7,8,9}

Awesome blog. Great work dude .

This Best website I have seen for java interview preparation

intro-to-java-programming

Solutions to introduction to java programming by y. daniel liang. 10th edition, introduction to java programming 10th edition exercise solutions.

This repo contains my solutions to the end-of-chapter exercise’s from Y. Daniel Liang’s Intro to Java Programming (10th Edition)

I’ve included links below to all the freely accessible companion material and quick links to navigate through my solutions by chapter., see contribution guide for coding guidelines and information on how to contribute., - about the 10th edition -.

“Daniel Liang teaches concepts of problem-solving and object-oriented programming using a fundamentals-first approach . Beginning programmers learn critical problem-solving techniques then move on to grasp the key concepts of object-oriented, GUI programming, advanced GUI and Web programming using Java…“

Companion Content

Additional online learning material that came with the books, bonus chapters online, exercise check tool, video notes, self-check chapter quiz’s, hints to quizzes and programming projects, checkpoint answers, uml diagrams for chapter 9 - 13, example programs by chapter, algorithm animations, java coding style guidelines, how to contribute, coding guidelines, solution must use java 8 se, as this is the version used by the book., every solution should have a java file containing a public main method for testing it., naming convention is: exercisecc_ee.java where cc is the chapter number and ee is the exercise number., the public exercise class containing the main method must include a javadoc comment on the class with original exercise question., each solution should be its own self-contained program with minimal dependencies on other files. if you need multiple files please create a package for the exercise., ch_xx/exercise22_07/exercise22_07.java, this allows us to utilize the exercise checking tool exercise checking tool to verify solutions., example exercise solution:, pull requests:.

To add new solutions, that do not already exist.
To add new documentation and/or comments to existing exercise solutions.
Fork the Master branch
Create a feature branch (with a descriptive name) using the fork from step 1.
Make your changes to your new branch (Only commit and push the files you plan to merge).
Make a Pull Request into our intro-to-java-programming Master branch.
Be sure to include the Chapter and Exercise number.
To request a change to an existing solution.
You find an error in an existing solution.

Exercise Solutions:

Quick links to navigate these solutions by chapter, indicates 100% completion of all exercises for that chapter.

Exercises Needed: 13, 15, 17, 19, 21, 23, 25, 27, 29, 31

Chapter 22 - Developing Efficient Algorithms
Chapter 23 - Sorting
Chapter 24 - Implementing Lists, Stacks, Queues, and Priority Queues
Chapter 25 - Binary Search Trees
--> Chapter 26 --> - AVL Trees
Chapter 27 - Hashing
Chapter 28 - Graphs and Applications
Chapter 29 - Weighted Graphs and Applications
Chapter 30 - Multithreading and Parallel Programming
Chapter 31 - Networking
--> Chapter 32 --> - Java Database Programming
--> Chapter 33 --> - Java Server Faces

Checkpoint Questions at the end of each chapter

Chapter 1 check point questions, chapter 2 check point questions, chapter 3 check point questions, chapter 4 check point questions, chapter 5 check point questions, chapter 6 check point questions, chapter 7 check point questions, chapter 8 check point questions, chapter 9 check point questions, chapter 10 check point questions, chapter 11 check point questions, chapter 12 check point questions, chapter 13 check point questions, chapter 14 check point questions, chapter 15 check point questions, chapter 16 check point questions, chapter 17 check point questions, chapter 18 check point questions, chapter 19 check point questions, chapter 20 check point questions, chapter 21 check point questions, chapter 22 check point questions, chapter 23 check point questions, chapter 24 check point questions, chapter 25 check point questions, chapter 26 check point questions, chapter 27 check point questions, chapter 28 check point questions, chapter 29 check point questions, chapter 30 check point questions, chapter 31 check point questions, chapter 32 check point questions, chapter 33 check point questions, chapter 34 check point questions, chapter 35 check point questions, chapter 36 check point questions, chapter 37 check point questions, chapter 38 check point questions, chapter 39 check point questions, chapter 40 check point questions, chapter 41 check point questions, chapter 42 check point questions, chapter 43 check point questions, chapter 44 check point questions, chapter 45 check point questions, self-check quiz's, self-check quiz's are provided for self testing and reinforcing what you leaned in the chapter, chapter 1 self-check quiz, chapter 2 self-check quiz, chapter 3 self-check quiz, chapter 4 self-check quiz, chapter 5 self-check quiz, chapter 6 self-check quiz, chapter 7 self-check quiz, chapter 8 self-check quiz, chapter 9 self-check quiz, chapter 10 self-check quiz, chapter 11 self-check quiz, chapter 12 self-check quiz, chapter 13 self-check quiz, chapter 14 self-check quiz.

Think Java: How To Think Like a Computer Scientist - 2e

(8 reviews)

Chris Mayfield, James Madison University

Allen Downey, Franklin W. Olin College of Engineering

ISBN 13: 9781491929568

Publisher: Green Tea Press

Language: English

Formats Available

Conditions of use.

Learn more about reviews.

Reviewed by Jeffrey LaMarche, Special Purpose Instructor, Radford University on 1/13/22

Comprehensiveness rating: 4 see less

The book covers most topics that I would expect in a CS1 level course. One topic that is strangely missing is working with text files, which is something that can lead to more interesting beginning programs. The chapters themselves are fairly short and do not always cover all of the information that might be expected. This also means that there are a limited number of examples available for the students to look at. Some information is also not covered where it might be expected either. For example, the increment and decrement operators are not covered until chapter six, which is about loops.

Content Accuracy rating: 4

The book is very accurate. I do not remember encountering any specific errors in the text or code provided. There might be some bias, which is because most programmers are biased about the way that they do things (e.g., Java programmers tend to go about coding differently than C++ programmers, etc.). I know that I disagreed with a few things in the book, and it was also very minor in the grand scheme of everything.

Relevance/Longevity rating: 3

I think that this book will stay relevant for a while. The problems are with updating and modularity (see below). Adding in new features, such as Java Records, could take extensive work. (I do not think Records are really needed and some of my colleagues disagree.)

Clarity rating: 4

The book is very easy to read and follow. I would say that additional examples might be helpful in some areas, since only providing a single context is not always effective for reaching a large amount of students.

Consistency rating: 5

The book adheres to a consistent excellent style and grammatical framework.

Modularity rating: 3

This book, like most computer programming books, has modularity issues. Some chapters heavily rely on other chapters, so reordering the readings is challenging. Reordering or omitting chapters can also be problematic, because that content might be referenced later.

Organization/Structure/Flow rating: 4

The book has great organization throughout. Sometimes I would have introduced things in a different order within a section or moved topics to different sections that made more sense to me.

Interface rating: 4

The score for the interface varies a little depending on which version of the textbook is being used. The HTML version viewable from Green Tea Press has an alert that not all mathematical symbols might display correctly. The HTML Trinket version does not have this alert, however it does not have as good of a table of contents with direct links right to the sections like the Green Tea Press version. The actual mathematical operator symbols are not listed in the index, which might be confusing to some students if they wanted to refer to them.

Grammatical Errors rating: 5

I do not remember there being any grammatical errors during my reading of the book.

Cultural Relevance rating: 5

I do not recall there being anything insensitive or offensive in the book. It is possible that the example contexts could be expanded to be more inclusive of more backgrounds. This could be as simple as changing from using playing cards as an example and switching to using dice instead.

The book mentions using Dr. Java in the appendix, which is something that I thought about bringing up in the relevance area. I used to use Dr. Java for my CS1 courses and I liked it greatly. Eventually, I could no longer get it to work on Mac OS X, so I stopped using it. The last update to Dr. Java was also in 2019, which means that development on it might no longer be active.

Reviewed by Peter Morgan, Adjunct Professor, Bunker Hill Community College on 6/27/20

The book is appropriate for a first semester Computer Science course, although it does not present every detail that a Computer Science professor may wish to cover in a first semester programming course. The instructor should plan to fill in small details in lecture or with supplementary reading, if those details are needed for whatever programming projects they wish to assign to the students.

Content Accuracy rating: 5

Having taught using this book for two semesters, I cannot think of any inaccuracies.

Relevance/Longevity rating: 5

The book begins by walking the reader through the mechanics of writing a very simple Java program. Throughout the book, the focus is on key concepts that a beginning Computer Science student needs to understand. The text also refers the reader to online reference materials, such as the Java Tutorial (https://docs.oracle.com/javase/tutorial/), where the student can find more detailed information.

Clarity rating: 5

I have had student feedback indicating that they found the book clear and easy to read.

I cannot think of ANY inconsistency.

Modularity rating: 4

The chapters are fairly short, making each one approximately appropriate for one week of classes.

Each chapter concludes with a summary of the vocabulary introduced in the chapter, as well as a number of exercises. There are several useful Appendices, and the sample programs that appear in the text are available for free download. The book introduces a few concepts, such as recursion and inheritance, that some Computer Science departments may choose to defer to a follow-on (second semester) course. These are easy enough to de-emphasize, without sacrificing any continuity. It is also possible that a brief mention of a more advanced topic will encourage the students’ curiosity about Computer Science in general.

Interface rating: 5

No issues found. As far as I know, all of the URLs to other resources are up to date.

No problems observed.

No problems found.

Java is an evolving language, so it would be impossible for any introductory textbook to cover every topic that a Java programmer is likely to encounter. However, this book provides a reader-friendly starting point, with helpful of links to more comprehensive resources.

Reviewed by George Foster, Adjunct Instructor, University of Mary Washington on 4/30/19

Comprehensiveness rating: 5 see less

I have used "Think Java" previously as a supplement to my notes in my sections of an introductory programming and problem solving CS1 level course in Java, and intend to do so again, but to emphasize use of the textbook more. The textbook covers all of the material required in CS1 except for File I/O. The text takes a "late objects" approach, mentioning just the minimum required about classes to explain how to write the first program. Search, sort, and recursion are covered. The table of contents and index provide a good road map to find topics of interest. Each chapter includes both a vocabulary list and a sample problem section.

Errors I had noticed in prior versions of the text have been corrected. Vocabulary is used in industry-standard fashion. All mentions of specific Java IDEs and tools are informational and relatively free of judgement.

While the field of computer science is constantly evolving, the approach taken by this text to teach the fundamentals is likely to survive. The newer features of the language in Java 9 and above are topics I would expect to see in the next course (CS2) beyond this textbook. That said, the inclusion of the Java2D features in the appendix may become dated if JavaFx truly takes off.

My primary reason for choosing this textbook is the conciseness and the clarity. The language used is straight-forward and direct, and the examples are very helpful. The vocabulary is defined both in context and in a separate vocabulary section. I can't say enough about the benefits of a concise textbook when a student is searching for one critical piece of information to cement his or her understanding of a concept. The only section where I have any issue with clarity is the discussion of higher-order, machine language, and byte code in section 1.3.

The textbook is highly consistent in both terminology and structure. The vocabulary sections ensure that all sections of the text access the concepts with the same terminology.

Modularity rating: 5

The textbook is about as modular as can be given the need for fundamental programming topics to build upon each other. The chapters are sufficiently small and further subdivided into bite-sized chunks. However, some of the authors' choices in topic order are locked in. For example, the authors choose to cover loops before arrays, and as a result use loops all through the material in the chapter on arrays, even though there may be other options to teach arrays that do not require the use of loops. Some of the more advanced material near the end and especially the appendices can be skipped without disruption.

Organization/Structure/Flow rating: 5

The organization of the text is logical and flows well from section to section. The structure of each chapter makes it easy to navigate the text and find the required information.

I've used both the PDF and web versions of the text with no problems. The addition of even just a fancier cover would help with providing a more professional textbook appearance that the quality of the textbook deserves.

The textbook has been thoroughly edited.

The examples used are cross-cultural, although a surprising number of students in recent years are unfamiliar with standard card games.

"Think Java" covers the material for a CS1 class with just the right depth. The concise writing style, clear vocabulary definitions, and helpful examples make this text the right fit for my class.

Reviewed by Isabela Hidalgo, Instructor I, University of South Florida on 3/27/18

Concepts are presented individually, in a fundamentals-first approach, with examples that are simple for students who are learning to program for the first time. It does not assume any previous knowledge of programming or college-level math. It presents the concepts well, without overwhelming the reader with long and complicated examples. It covers the topics for a fundamentals of programming course and even a good introduction to Object-Oriented Programming.

All the code is available on GitHub and instructions to use GitHub are provided in the book. It is a good way to give students some experience using code repositories. The exercises are at the right difficulty level to give students some practice.

The vocabulary section at the end of each chapter is useful.The index and table of contents are complete.

I have not found any conceptual errors in the book.

The basic programming concepts in the book will continue to be relevant. The code, tested in Java 8 (in book’s edition 6.1.3), should continue to work with new Java releases. New developments in the programming language can be added in newer editions.

The explanations and examples are clear and easy to follow. The exercise objectives and instructions are easy to understand, not confusing or intimidating. The terms are well-defined and the examples are familiar. The vocabulary section in each chapter is a valuable resource for students who need to review the terminology.

It is great that the author updated the textbook in response to the previous reviews. The book is very consistent now, with introductions in every chapter, as well as exercises and vocabulary. The introduction to OOP was moved to chapter 10 and the section on Java documentation was also moved to an earlier chapter. The terminology used is consistent throughout the book too.

The book is now divided in 14 chapters and 3 appendices. The size and section breakdown is good for a semester-long CS1 course. Some advanced topics can be skipped without disruption. The book is not overly verbose which gives students more time to work on their programs. Every chapter has well-defined exercises and students are encouraged to work on all of them.

The book is well organized and the topics flow in a logical fashion. Some of the issues from previous editions have been fixed. Introductions to every chapter are now available. My suggestion is to add a clear list of student outcomes for each chapter. That would be useful for students and instructors alike.

I reviewed the PDF version and it looks good. The links in the table of contents are working. There are clickable links within the text to different sections, such as appendices, and external websites. Having the code printed in color is very helpful. I also like that when a Java keyword is mentioned in the explanations, the font (face and color) of the keyword matches the font in the code samples.

I have not found any grammatical errors.

The text is neutral. The examples are current and unbiased. I have not found any insensitive references.

I found the book to be very accessible to the first-time programmer. It presents programming logic with simple, short examples. I intend to use it in my introduction course.

Reviewed by Vijayalakshmi Ramasamy, Visiting Assistant Professor, Miami University on 2/1/18

“Think Java” intends to provide all the topics needed for the beginners to learn Java programming. The vocabulary, comprehensive index, a variety of practice exercises at the end of each chapter, and the links to related material stimulate the interest to learn. However, the text does not include a precise introduction and a concluding summary in many chapters. A sorted list of the vocabulary of all the terms can be presented as a glossary before the index.

The content is correct, easy to follow. In the online version, the text for the following hyperlink shows ?? in Section 1.10. http://greenteapress.com/thinkjava6/html/thinkjava6001.html#code

Any textbook on programming concepts needs to reflect the evolution in the field by updating it periodically. It is essential to keep the users updated by extending a reference to the current Java 9 API documentation.

The author employs a clear and readable writing style with easy-to-follow illustrations.

Consistency rating: 4

The vocabulary section at the end of each chapter is neither sorted nor precise in some definitions. The definition of the term 'void method' is included in the vocabulary section of the value methods chapter.

The textbook consists of organized and manageable sections and sub-sections. Still, the void and value methods may be merged into a single chapter to enable readability and ensure continuity.

The text presents all the relevant information needed for a beginner progressively with a few structural issues. The sections in some chapters are not organized with smoothly flowing content. For instance, Chapter 2 entitled "Variables and Operators" does not introduces all the most basic data types. A list of all the operators in Java is not presented in the same chapter. The modulus, relational, and unary increment and decrement operators are introduced in Chapters 3, 5, and 7 respectively.

The text flows clean and includes a useful collection of web-links for relevant reading material. The online version enhances both readability and interest by linking one concept to another.

No grammatical errors found.

The textbook is culturally unbiased.

Overall, the availability of the text in pdf, online and printed forms makes it a useful resource for the post-secondary learners.

Reviewed by Debra Duke, Instructor, Virginia Commonwealth University on 2/8/17

The textbook covers all of topics for a post-secondary introduction to programming course in Java (CS1). The topics are presented in a "late objects" order. Each chapter includes a Vocabulary section that is a glossary of the terms introduced in... read more

The content is completely accurate, error-free, and unbiased.

Relevance/Longevity rating: 4

The computer science concepts are up-to-date, generally. The only error that I found was with a link to the development tool, Checkstyle, in Appendix A. The project has moved from sourceforge.net to github at https://github.com/checkstyle/checkstyle. Because this was located in the Development Tools appendix, it should be easy to update in a future release.

One of the strengths of Think Java is how easily understood the writing is. Keeping the language clear is critical in explaining complex computer science concepts and this book does an excellent job.

I found it to be very consistent.

Reading sections are broken up into sections that are clearly distinguished in the table of contents. This is helpful if you choose to skip, for example, sections 5.8 Recursive methods and 5.9 Recursive stack diagrams because you don't teach recursion until the following semester.

Think Java is very well organized. It covers the core computer science topics using the Java programming language, while gently introducing more advanced concepts, such as the description of Java as a Turing complete programming language in section 6.7.

I read the book with iBook reader on my iPad and MacBook. In both cases it was very easy to navigate and all of the figures appeared correctly. I tested it briefly in Acrobat Reader and had no issues with navigating to the various sections.

I found no grammatical errors.

Cultural Relevance rating: 4

I found the tone culturally neutral. The examples are mathematics based or with familiar objects, such as a deck of cards.

Reviewed by Bradford Armitage, Adjunct Professor, Metropolitan State University on 8/21/16

The book does a great job on providing fundamental programming concepts in a manner that will make it easy for Students to grasp. Materials are organized in a reasonable manner, although the chapter on loops could be presented sooner. Each chapter ends with Glossary to further help explain the terms used in the chapter. Each chapter had a good amount of exercises at the end. Overall, the book is very well done, and one that I would use in the classroom.

I did not find any errors. I reviewed about 80% of the presented code, and could not find any issues.

The book’s concepts on programming fundamentals will be long lasting. Java may change with new Versions, but the code/syntax presented in this book is standard stuff, so it also should be long lasting (at least as long as Java is in use).

The author is very deliberate in his explanations of using Java in solving problems and in the overall programming concepts. The author does a very good job with presenting examples and explaining in detail each part of the example. Also there is a consistency in how each example, or programming concept is presented.

As stated in the clarity part of the review, the author is very consistent in how he presents examples and concepts. This is one of the strong points of the book, along with the easy simplistic way things are presented. Very easy for Students to see the concept being presented and to understand how it is coded in Java. Some text books over complicate the example, that is not the case in this book.

The text contains 16 chapters and four appendixes. All the chapters were fairly short in size, so that a Student would not get over whelmed with anyone concept. Each chapter was broken down into concise parts, so that an instructor could easily assign the whole chapter or sub-sections. The chapters are arranged in an order, such that the Student can easily flow from one concept to the next, if reading the book in sequence. The one issue, the chapter on Loops should be presented earlier.

Please refer to the comments in the modularity section. Overall, book is very well organized and structured to the point a Student should have no issue going through the book and following the concepts from one to the other.

The text was very clean and loaded with links to relevant material. The book would benefit if there were some links with in the text to assist in navigation. So one concept or example could be linked to another.

Did not find any grammar errors. Assume the text has been scanned multiple times by now.

The text deals with programming fundamentals, Java syntax, and logic. Not much in the way of cultural relevance in this topic, so it should not be offensive to any group.

Overall very impressed with the book and definitely one I would use in my classroom.

Reviewed by Siva Jasthi, Adjunct Faculty, Metropolitan State University on 8/21/16

It has covered the topics that are expected to be covered in a beginning programming course. However, the structure and arrangement of the material is not smooth. Consistency in presentation is missing. read more

It is accurate, error-free and unbiased.

The links to the java documentation are provided with explicit URLs. It is unavoidable to update these when a new version of Java is released.

The life of programming text books is directly related to the evolution of the programming languages. For example, the latest version of Java is Java 8 and this text book is referring to Version 6.

Abstraction (giving and seeing big picture) is very important concept in Java. Some treatment with real world examples would be useful.

Some sub-sections in the individual chapters are out of place. For example "(8.5) Reading Documentation" is applicable to any chapter. It is best to cover and provide details on how to search and navigate java documentation in general in the first chapter itself.

It would be good to cover "Chapter 15. Object oriented programming" prior to chapters 12,13, 14.

Consistency rating: 2

This book lacks consistency. Many chapters jump directly into the material while some chapters start with an introduction (example: 12 Arrays)

The text is well divided into chapters, sections and sub-sections

Organization/Structure/Flow rating: 2

It is expected that each chapter starts with the goals of that chapter. "What is covered? What will I learn? Why should I read this chapter?" -- these questions should be addressed in the first few paragraphs of each chapter.

Many chapter directly jump to the topic and only a couple of chapters have this introduction.

Interface rating: 3

Here are some issues I have found

While navigating the PDF, I can jump to a topic by clicking on the page number in the INDEX. However, you can not do the same thing from TABLE OF CONTENTS. It is very limiting to manually nagivate using "page down" or "search"

Didn't find any issues.

There are no offensive or insensitive references.

Chapters (3) and (6) can be combined into "methods". All the concepts explained in these two chapters are same with one distinguishing feature - one type returns nothing. Another type returns something. Rest of the concepts are same.

1 Computer Programming
2 Variables and Operators
3 Input and output
4 Methods and Testing
5 Conditionals and logic
6 Loops and Strings
7 Arrays and References
8 Recursive Methods
9 Immutable Objects
10 Mutable Objects
11 Designing Classes
12 Arrays of Objects
13 Objects of Arrays
14 Extending Classes
15 Arrays of Arrays
16 Reusing Classes
17 Advanced Topics
D Debugging

Ancillary Material

Green Tea Press

About the Book

Think Java is a hands-on introduction to computer science and programming used by many universities and high schools around the world. Its conciseness, emphasis on vocabulary, and informal tone make it particularly appealing for readers with little or no experience. The book starts with the most basic programming concepts and gradually works its way to advanced object-oriented techniques.

In this fully updated and expanded edition, authors Allen Downey and Chris Mayfield introduce programming as a means for solving interesting problems. Each chapter presents material for one week of a college course and includes exercises to help you practice what you’ve learned. Along the way, you’ll see nearly every topic required for the AP Computer Science A exam and Java SE Programmer I certification.

About the Contributors

Chris Mayfield , PhD, is an Assistant Professor of Computer Science at James Madison University. His research focuses on CS education and professional development, particularly in K-12 schools. Over the past several years, he has taught introductory CS courses using POGIL and the flipped classroom.

Allen Downey is an American computer scientist, Professor of Computer Science at the Franklin W. Olin College of Engineering and writer of free textbooks.

Downey received in 1989 his BS and in 1990 his MA, both in Civil Engineering from the Massachusetts Institute of Technology, and his PhD in Computer Science from the University of California at Berkeley in 1997.

He started his career as Research Fellow in the San Diego Supercomputer Center in 1995. In 1997 he became Assistant Professor of Computer Science at Colby College, and in 2000 at Wellesley College. He was Research Fellow at Boston University in 2002 and Professor of Computer Science at the Franklin W. Olin College of Engineering since 2003. In 2009-2010 he was also Visiting Scientist at Google Inc.

Contribute to this Page

How to think like a programmer — lessons in problem solving

by Richard Reis

If you’re interested in programming, you may well have seen this quote before:

“Everyone in this country should learn to program a computer, because it teaches you to think.” — Steve Jobs

You probably also wondered what does it mean, exactly, to think like a programmer? And how do you do it??

Essentially, it’s all about a more effective way for problem solving .

In this post, my goal is to teach you that way.

By the end of it, you’ll know exactly what steps to take to be a better problem-solver.

Why is this important?

Problem solving is the meta-skill.

We all have problems. Big and small. How we deal with them is sometimes, well…pretty random.

Unless you have a system, this is probably how you “solve” problems (which is what I did when I started coding):

Try a solution.
If that doesn’t work, try another one.
If that doesn’t work, repeat step 2 until you luck out.

Look, sometimes you luck out. But that is the worst way to solve problems! And it’s a huge, huge waste of time.

The best way involves a) having a framework and b) practicing it.

“Almost all employers prioritize problem-solving skills first.

Problem-solving skills are almost unanimously the most important qualification that employers look for….more than programming languages proficiency, debugging, and system design.

Demonstrating computational thinking or the ability to break down large, complex problems is just as valuable (if not more so) than the baseline technical skills required for a job.” — Hacker Rank ( 2018 Developer Skills Report )

Have a framework

To find the right framework, I followed the advice in Tim Ferriss’ book on learning, “ The 4-Hour Chef ”.

It led me to interview two really impressive people: C. Jordan Ball (ranked 1st or 2nd out of 65,000+ users on Coderbyte ), and V. Anton Spraul (author of the book “ Think Like a Programmer: An Introduction to Creative Problem Solving ”).

I asked them the same questions, and guess what? Their answers were pretty similar!

Soon, you too will know them.

Sidenote: this doesn’t mean they did everything the same way. Everyone is different. You’ll be different. But if you start with principles we all agree are good, you’ll get a lot further a lot quicker.

“The biggest mistake I see new programmers make is focusing on learning syntax instead of learning how to solve problems.” — V. Anton Spraul

So, what should you do when you encounter a new problem?

Here are the steps:

1. Understand

Know exactly what is being asked. Most hard problems are hard because you don’t understand them (hence why this is the first step).

How to know when you understand a problem? When you can explain it in plain English.

Do you remember being stuck on a problem, you start explaining it, and you instantly see holes in the logic you didn’t see before?

Most programmers know this feeling.

This is why you should write down your problem, doodle a diagram, or tell someone else about it (or thing… some people use a rubber duck ).

“If you can’t explain something in simple terms, you don’t understand it.” — Richard Feynman

Don’t dive right into solving without a plan (and somehow hope you can muddle your way through). Plan your solution!

Nothing can help you if you can’t write down the exact steps.

In programming, this means don’t start hacking straight away. Give your brain time to analyze the problem and process the information.

To get a good plan, answer this question:

“Given input X, what are the steps necessary to return output Y?”

Sidenote: Programmers have a great tool to help them with this… Comments!

Pay attention. This is the most important step of all.

Do not try to solve one big problem. You will cry.

Instead, break it into sub-problems. These sub-problems are much easier to solve.

Then, solve each sub-problem one by one. Begin with the simplest. Simplest means you know the answer (or are closer to that answer).

After that, simplest means this sub-problem being solved doesn’t depend on others being solved.

Once you solved every sub-problem, connect the dots.

Connecting all your “sub-solutions” will give you the solution to the original problem. Congratulations!

This technique is a cornerstone of problem-solving. Remember it (read this step again, if you must).

“If I could teach every beginning programmer one problem-solving skill, it would be the ‘reduce the problem technique.’

For example, suppose you’re a new programmer and you’re asked to write a program that reads ten numbers and figures out which number is the third highest. For a brand-new programmer, that can be a tough assignment, even though it only requires basic programming syntax.

If you’re stuck, you should reduce the problem to something simpler. Instead of the third-highest number, what about finding the highest overall? Still too tough? What about finding the largest of just three numbers? Or the larger of two?

Reduce the problem to the point where you know how to solve it and write the solution. Then expand the problem slightly and rewrite the solution to match, and keep going until you are back where you started.” — V. Anton Spraul

By now, you’re probably sitting there thinking “Hey Richard... That’s cool and all, but what if I’m stuck and can’t even solve a sub-problem??”

First off, take a deep breath. Second, that’s fair.

Don’t worry though, friend. This happens to everyone!

The difference is the best programmers/problem-solvers are more curious about bugs/errors than irritated.

In fact, here are three things to try when facing a whammy:

Debug: Go step by step through your solution trying to find where you went wrong. Programmers call this debugging (in fact, this is all a debugger does).

“The art of debugging is figuring out what you really told your program to do rather than what you thought you told it to do.”” — Andrew Singer

Reassess: Take a step back. Look at the problem from another perspective. Is there anything that can be abstracted to a more general approach?

“Sometimes we get so lost in the details of a problem that we overlook general principles that would solve the problem at a more general level. […]

The classic example of this, of course, is the summation of a long list of consecutive integers, 1 + 2 + 3 + … + n, which a very young Gauss quickly recognized was simply n(n+1)/2, thus avoiding the effort of having to do the addition.” — C. Jordan Ball

Sidenote: Another way of reassessing is starting anew. Delete everything and begin again with fresh eyes. I’m serious. You’ll be dumbfounded at how effective this is.

Research: Ahh, good ol’ Google. You read that right. No matter what problem you have, someone has probably solved it. Find that person/ solution. In fact, do this even if you solved the problem! (You can learn a lot from other people’s solutions).

Caveat: Don’t look for a solution to the big problem. Only look for solutions to sub-problems. Why? Because unless you struggle (even a little bit), you won’t learn anything. If you don’t learn anything, you wasted your time.

Don’t expect to be great after just one week. If you want to be a good problem-solver, solve a lot of problems!

Practice. Practice. Practice. It’ll only be a matter of time before you recognize that “this problem could easily be solved with <insert concept here>.”

How to practice? There are options out the wazoo!

Chess puzzles, math problems, Sudoku, Go, Monopoly, video-games, cryptokitties, bla… bla… bla….

In fact, a common pattern amongst successful people is their habit of practicing “micro problem-solving.” For example, Peter Thiel plays chess, and Elon Musk plays video-games.

“Byron Reeves said ‘If you want to see what business leadership may look like in three to five years, look at what’s happening in online games.’

Fast-forward to today. Elon [Musk], Reid [Hoffman], Mark Zuckerberg and many others say that games have been foundational to their success in building their companies.” — Mary Meeker ( 2017 internet trends report )

Does this mean you should just play video-games? Not at all.

But what are video-games all about? That’s right, problem-solving!

So, what you should do is find an outlet to practice. Something that allows you to solve many micro-problems (ideally, something you enjoy).

For example, I enjoy coding challenges. Every day, I try to solve at least one challenge (usually on Coderbyte ).

Like I said, all problems share similar patterns.

That’s all folks!

Now, you know better what it means to “think like a programmer.”

You also know that problem-solving is an incredible skill to cultivate (the meta-skill).

As if that wasn’t enough, notice how you also know what to do to practice your problem-solving skills!

Phew… Pretty cool right?

Finally, I wish you encounter many problems.

You read that right. At least now you know how to solve them! (also, you’ll learn that with every solution, you improve).

“Just when you think you’ve successfully navigated one obstacle, another emerges. But that’s what keeps life interesting.[…]

Life is a process of breaking through these impediments — a series of fortified lines that we must break through.

Each time, you’ll learn something.

Each time, you’ll develop strength, wisdom, and perspective.

Each time, a little more of the competition falls away. Until all that is left is you: the best version of you.” — Ryan Holiday ( The Obstacle is the Way )

Now, go solve some problems!

And best of luck ?

Special thanks to C. Jordan Ball and V. Anton Spraul . All the good advice here came from them.

Thanks for reading! If you enjoyed it, test how many times can you hit in 5 seconds. It’s great cardio for your fingers AND will help other people see the story.

If this article was helpful, share it .

Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started

Streamline hiring withour effortless screening.

Optimise your hiring process with HiPeople's AI assessments and reference checks.

Are you ready to conquer the challenges of Tricky Java Interview Questions? Whether you're aiming for that dream job or seeking to level up your Java skills, this guide has you covered.

Dive into the world of complex Java queries, unravel their intricacies, and emerge as a confident and proficient Java developer. Let's unravel the secrets to mastering those tricky interview questions!

What are Tricky Java Interview Questions?

Tricky Java interview questions are not your typical run-of-the-mill inquiries. These questions are designed to test your in-depth knowledge of Java, problem-solving skills, and ability to think critically under pressure. They often go beyond the basics and challenge you to demonstrate a deep understanding of the language, its nuances, and its application in real-world scenarios.

Characteristics of Tricky Java Interview Questions

Complexity: Tricky questions may involve intricate scenarios, multiple concepts, or unusual edge cases.
Problem-Solving: They often require creative problem-solving and the ability to devise efficient solutions.
Application: These questions may assess your ability to apply Java concepts to practical situations.
Critical Thinking: Expect questions that demand critical thinking and the ability to identify potential pitfalls.
Depth of Knowledge: Tricky questions may probe your understanding of advanced Java topics and best practices.

Importance of Java Interviews

Java interviews hold significant importance for both job seekers and employers.

For Job Seekers

Career Opportunities: Mastering Java can open doors to a wide range of job opportunities in software development, backend engineering, mobile app development, and more.
Higher Compensation: Companies often offer competitive salaries to skilled Java developers due to the language's widespread use and demand.
Skill Validation: Success in Java interviews validates your expertise and serves as a testament to your capabilities.

For Employers

Quality Talent Acquisition: Java interviews help companies identify and hire talented individuals who can contribute effectively to their projects.
Code Quality: Hiring skilled Java developers results in higher-quality code, which is critical for the success and maintainability of software systems.
Productivity: Experienced Java developers tend to be more productive and require less training, saving companies time and resources.

Preparing for Tricky Java Interviews

Preparing for tricky Java interviews requires a structured and focused approach. Here are some steps to help you get ready:

Review Core Concepts: Ensure your foundational knowledge of Java is strong, including object-oriented programming, data types, and control structures.
Explore Advanced Topics: Delve into advanced Java topics like multithreading, design patterns, and Java Virtual Machine (JVM) internals.
Practice Coding: Regularly practice coding exercises and challenges to sharpen your problem-solving skills.
Read Java Documentation: Familiarize yourself with the official Java documentation to understand standard libraries and best practices.
Mock Interviews: Consider participating in mock interviews to simulate real interview scenarios and receive feedback.
Stay Updated: Stay abreast of Java updates and industry trends to demonstrate your commitment to continuous learning.

Common Interview Formats

Java interviews come in various formats, each with its own focus and objectives. Here's an overview of common interview formats you might encounter:

Technical Assessment: You may be asked to complete coding challenges or technical tests online, focusing on your coding skills and problem-solving abilities.
Behavioral Interview: In this format, the interviewer evaluates your soft skills, teamwork, and how you handle various workplace scenarios.
Whiteboard Coding: You might need to solve coding problems on a whiteboard or explain your approach verbally, emphasizing problem-solving skills.
Panel Interview: Multiple interviewers assess your technical knowledge, problem-solving skills, and cultural fit within the company.
Take-Home Assignment: You receive a coding assignment to complete at home within a specified timeframe, demonstrating your coding proficiency and time management.

Understanding these interview formats can help you tailor your preparation to the specific requirements of your upcoming Java interview.

Core Java Concepts

Let's dive into the fundamental concepts of Java that are crucial for acing those tricky interviews.

Object-Oriented Programming Principles

Object-oriented programming (OOP) is the backbone of Java. It's essential to understand how objects and classes work together.

Classes and Objects

In Java, everything revolves around classes and objects. A class is a blueprint for creating objects, while objects are instances of classes. Here's a simple example:

class Car { String brand; int year; void start() { System.out.println("Car started!"); } } public class Main { public static void main(String[] args) { Car myCar = new Car(); myCar.brand = "Toyota"; myCar.year = 2020; myCar.start(); } }

In this example, we define a Car class with attributes brand and year , along with a start method. We then create an instance of the Car class and use it to access the class's members.

Inheritance and Polymorphism

Inheritance allows one class to inherit the attributes and methods of another class. Polymorphism enables objects to take on multiple forms.

class Animal { void makeSound() { System.out.println("Some sound"); } } class Dog extends Animal { @Override void makeSound() { System.out.println("Woof!"); } } public class Main { public static void main(String[] args) { Animal myDog = new Dog(); myDog.makeSound(); // Outputs "Woof!" } }

Here, the Dog class inherits from the Animal class and overrides the makeSound method to provide a specific implementation.

Java Data Types and Variables

Java supports various data types, which determine the kind of data that can be stored in a variable.

Primitive Data Types

int: Represents whole numbers.
double: Represents floating-point numbers.
char: Represents a single character.
boolean: Represents true or false values.

int age = 25; double salary = 55000.50; char grade = 'A'; boolean isJavaFun = true;

Reference Data Types

Reference data types hold references (memory addresses) to objects. Common reference data types include arrays, strings, and user-defined classes.

String name = "John"; int[] numbers = {1, 2, 3, 4, 5};

Control Flow Statements

Control flow statements allow you to control the execution of your Java code.

Conditional Statements

Conditional statements, like if , else if , and else , help you make decisions in your code.

int score = 85; if (score >= 90) { System.out.println("Excellent!"); } else if (score >= 70) { System.out.println("Good job!"); } else { System.out.println("Keep practicing."); }

Looping Statements

Looping statements, including for , while , and do-while , allow you to repeat tasks.

for (int i = 1; i <= 5; i++) { System.out.println("Iteration " + i); } int count = 0; while (count < 3) { System.out.println("Count: " + count); count++; }

Exception Handling

Exception handling in Java is crucial for robust and error-free code.

Try-Catch Blocks

try { // Code that may throw an exception int result = 10 / 0; // This will throw an ArithmeticException } catch (ArithmeticException e) { // Handle the exception System.out.println("An error occurred: " + e.getMessage()); }

Custom Exceptions

You can create custom exceptions to handle specific error scenarios effectively.

class MyCustomException extends Exception { public MyCustomException(String message) { super(message); } } public class Main { public static void main(String[] args) { try { throw new MyCustomException("This is a custom exception."); } catch (MyCustomException e) { System.out.println("Caught custom exception: " + e.getMessage()); } } }

Multithreading and Concurrency

Multithreading allows Java programs to execute multiple threads concurrently.

Input/Output (I/O) Operations

Input and output operations are essential for interacting with external data sources.

Java Fundamentals Interview Questions

1. what is the difference between == and .equals() in java for comparing objects.

How to Answer: Candidates should explain that == compares object references for equality, while .equals() is a method used to compare the content or value of objects. It's essential to mention that .equals() can be overridden by custom classes to provide a meaningful comparison based on object attributes.

Sample Answer: " == compares object references, checking if they point to the same memory location. In contrast, .equals() compares the actual content of objects. For instance, when comparing strings, .equals() checks if the character sequences are identical."

What to Look For: Look for candidates who understand the fundamental distinction between reference equality and content equality. They should also demonstrate knowledge of when and how to override the .equals() method in custom classes.

2. What are the differences between ArrayList and LinkedList in Java?

How to Answer: Candidates should highlight that ArrayList is backed by an array, provides fast random access, but has slower insertions and deletions. LinkedList uses a doubly linked list, excels in insertions/deletions, but is slower for random access. They should discuss use cases for each data structure.

Sample Answer: " ArrayList is based on an array, allowing fast random access. However, insertions and deletions are slower due to array resizing. LinkedList uses a doubly linked list, making insertions and deletions faster, but accessing elements sequentially is more efficient."

What to Look For: Look for candidates who can articulate the trade-offs between ArrayList and LinkedList and demonstrate when to use each data structure based on specific requirements.

3. Explain the significance of the static keyword in Java.

How to Answer: Candidates should describe that static denotes class-level members (variables or methods) that belong to the class, not instances. They should mention that static members can be accessed without creating an object of the class and are shared across all instances of the class.

Sample Answer: "The static keyword is used to define class-level members in Java. These members belong to the class itself, not to instances of the class. This means you can access static members without creating objects of the class, and changes to static variables are shared among all instances."

What to Look For: Look for candidates who can clearly explain the concept of static and provide examples of when and why it's useful, such as for constants or utility methods.

Object-Oriented Programming Interview Questions

4. what is the difference between an abstract class and an interface in java.

How to Answer: Candidates should explain that an abstract class can have both abstract (unimplemented) and concrete (implemented) methods, while an interface can only have abstract methods. They should also mention that a class can implement multiple interfaces but inherit from only one abstract class.

Sample Answer: "An abstract class can have both abstract and concrete methods, while an interface can only contain abstract methods. A class can implement multiple interfaces, but it can inherit from only one abstract class."

What to Look For: Look for candidates who can clearly articulate the distinctions between abstract classes and interfaces, understand their use cases, and explain when to prefer one over the other.

5. How does Java support multiple inheritance, and what is the "diamond problem"?

How to Answer: Candidates should discuss that Java supports multiple inheritance through interfaces, allowing a class to implement multiple interfaces. They should explain the "diamond problem" as a naming conflict when a class inherits methods with the same signature from multiple interfaces and how Java resolves it using interface method implementation.

Sample Answer: "Java supports multiple inheritance through interfaces, where a class can implement multiple interfaces. The 'diamond problem' occurs when a class inherits methods with the same signature from multiple interfaces. Java resolves this by requiring the implementing class to provide its implementation for the conflicting method."

What to Look For: Look for candidates who can explain how Java handles multiple inheritance and understand the challenges and solutions associated with the "diamond problem."

6. What are the access modifiers in Java, and how do they differ?

How to Answer: Candidates should list and describe the four main access modifiers in Java: public , private , protected , and default (no modifier). They should explain their visibility and accessibility rules within and outside the class hierarchy.

Sample Answer: "In Java, there are four access modifiers: public (accessible from anywhere), private (only within the same class), protected (within the same package and subclasses), and default (package-private, within the same package). They control the visibility and accessibility of class members."

What to Look For: Look for candidates who can clearly define access modifiers and provide examples of when and why each one is used.

Exception Handling Interview Questions

7. what is the difference between checked and unchecked exceptions in java.

How to Answer: Candidates should explain that checked exceptions are compile-time exceptions that must be handled using try-catch or declared with throws in the method signature. Unchecked exceptions, on the other hand, are runtime exceptions and do not require explicit handling.

Sample Answer: "Checked exceptions are exceptions that the compiler checks at compile-time, and you must either handle them using try-catch or declare them with throws in the method signature. Unchecked exceptions, also known as runtime exceptions, do not require explicit handling."

What to Look For: Look for candidates who can distinguish between checked and unchecked exceptions, understand their implications, and provide examples of each.

8. How does the finally block work in Java exception handling?

How to Answer: Candidates should explain that the finally block is used to ensure that a specific block of code is always executed, regardless of whether an exception is thrown or not. They should emphasize that it's commonly used for cleanup tasks like closing resources.

Sample Answer: "The finally block in Java ensures that a particular block of code is executed, whether an exception occurs or not. It's commonly used for tasks like closing files or releasing resources to guarantee proper cleanup."

What to Look For: Look for candidates who can articulate the purpose of the finally block and demonstrate an understanding of its role in exception handling and resource management.

Multithreading Interview Questions

9. what is synchronization in java, and why is it necessary.

How to Answer: Candidates should explain that synchronization in Java is used to control access to shared resources by multiple threads. They should mention that it prevents race conditions and ensures data consistency. Additionally, they should discuss synchronization mechanisms like synchronized methods and blocks.

Sample Answer: "Synchronization in Java is essential for controlling access to shared resources by multiple threads. It prevents race conditions and ensures data consistency. We achieve synchronization using synchronized methods or blocks to protect critical sections of code."

What to Look For: Look for candidates who can describe the importance of synchronization in multithreaded environments, provide examples of synchronization, and discuss potential issues like deadlock and how to avoid them.

10. Explain the difference between wait() , notify() , and notifyAll() methods in Java.

How to Answer: Candidates should describe that wait() is used by a thread to release the lock and enter a waiting state until another thread calls notify() or notifyAll() to wake it up. notify() wakes up one waiting thread, while notifyAll() wakes up all waiting threads.

Sample Answer: " wait() is used by a thread to release the lock and enter a waiting state until another thread calls notify() or notifyAll() . notify() wakes up one waiting thread, while notifyAll() wakes up all waiting threads, allowing them to compete for the lock."

What to Look For: Look for candidates who can explain the purpose and differences between wait() , notify() , and notifyAll() methods and demonstrate an understanding of their use in thread synchronization.

Advanced Java Concepts Interview Questions

11. what is the java memory model (jmm), and why is it important in multithreading.

How to Answer: Candidates should explain that the Java Memory Model (JMM) defines how threads interact with memory when reading and writing shared data. It's crucial for ensuring thread safety and preventing data inconsistencies in multithreaded programs.

Sample Answer: "The Java Memory Model (JMM) defines how threads interact with memory when reading and writing shared data. It's vital for ensuring thread safety and preventing data inconsistencies in multithreaded programs by specifying the order of memory operations."

What to Look For: Look for candidates who can articulate the significance of the Java Memory Model in multithreading and how it helps maintain data consistency.

12. How does Java support garbage collection, and what are the different types of garbage collectors?

How to Answer: Candidates should explain that Java supports automatic memory management through garbage collection. They should mention the types of garbage collectors in Java, such as the Serial, Parallel, and G1 collectors, and briefly describe their characteristics.

Sample Answer: "Java supports automatic memory management through garbage collection. There are various garbage collectors in Java, including the Serial, Parallel, and G1 collectors. Each has its own characteristics and is suitable for different scenarios."

What to Look For: Look for candidates who can discuss Java's garbage collection mechanisms, their advantages, and when to use specific types of garbage collectors.

13. What is the purpose of the Java Virtual Machine (JVM), and how does it execute Java programs?

How to Answer: Candidates should explain that the JVM is responsible for executing Java bytecode. They should describe the steps involved in the execution process, such as class loading, bytecode verification, and Just-In-Time (JIT) compilation.

Sample Answer: "The Java Virtual Machine (JVM) executes Java programs by loading classes, verifying bytecode, and then executing it. It uses Just-In-Time (JIT) compilation to convert bytecode into machine code for efficient execution."

What to Look For: Look for candidates who can provide a clear overview of the JVM's role in executing Java programs and explain key steps in the execution process.

14. What is Java's reflection API, and when is it used?

How to Answer: Candidates should describe that the reflection API in Java allows inspection and manipulation of classes, methods, fields, and objects at runtime. They should mention use cases, such as dynamic code generation, serialization, and frameworks like Spring.

Sample Answer: "Java's reflection API enables runtime inspection and manipulation of classes, methods, fields, and objects. It's used in scenarios like dynamic code generation, serialization, and in frameworks like Spring for dependency injection."

What to Look For: Look for candidates who can explain the purpose of the reflection API, provide examples of its use cases, and discuss its advantages and potential drawbacks.

15. Explain the concept of Java annotations and their practical applications.

How to Answer: Candidates should describe that Java annotations are metadata annotations that provide additional information about classes, methods, fields, or other program elements. They should discuss practical applications, such as code documentation, code generation, and framework configuration.

Sample Answer: "Java annotations are metadata annotations used to provide additional information about program elements. They have practical applications in code documentation, code generation, and configuring frameworks like Hibernate or Spring."

What to Look For: Look for candidates who can explain the concept of Java annotations, offer examples of their use in real-world scenarios, and discuss their benefits in code organization and automation.

Advanced Java Topics

Now, let's dive into some advanced Java topics that will set you apart in those challenging interviews.

Java Virtual Machine (JVM) Internals

Understanding the internal workings of the Java Virtual Machine (JVM) is crucial to write efficient and optimized Java code.

JVM Architecture

Class Loader: Loads class files into memory.
Execution Engine: Executes bytecode instructions.
Memory Areas: Includes methods, heap, stack, and more.
Native Interface: Allows interaction with native libraries.

Optimizing JVM performance involves configuring memory settings, garbage collection algorithms, and thread management. Profiling tools like VisualVM and JConsole can help identify bottlenecks.

Garbage Collection in Java

Java automatically manages memory through garbage collection (GC). Understanding GC mechanisms is vital for efficient memory usage.

GC Algorithms

Serial GC: Single-threaded, suitable for small applications.
Parallel GC: Multithreaded, for medium-sized applications.
Concurrent Mark-Sweep (CMS) GC: Low-latency collector.
Garbage-First (G1) GC: Balances throughput and latency.

By adjusting GC settings, you can optimize memory usage and reduce application pauses. Common parameters include heap size, GC algorithm selection, and thread counts.

Java Reflection

Java reflection allows you to inspect and manipulate classes, methods, fields, and constructors at runtime.

Reflection Basics

You can access class metadata, inspect annotations, and invoke methods dynamically. This is especially useful for frameworks like Spring.

Class<?> clazz = MyClass.class; Method[] methods = clazz.getDeclaredMethods(); for (Method method : methods) { System.out.println("Method Name: " + method.getName()); }

Reflection is employed in frameworks, libraries, and testing frameworks like JUnit. It enables features like dependency injection and dynamic loading.

Java Stream API

The Stream API introduced in Java 8 simplifies data processing and manipulation.

Stream Basics

Streams provide a concise way to filter, transform, and aggregate data in collections.

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5); int sum = numbers.stream() .filter(n -> n % 2 == 0) .mapToInt(Integer::intValue) .sum();

Stream Operations

Operations like filter , map , reduce , and collect make complex data operations more readable and efficient.

Java Lambda Expressions

Lambda expressions introduce functional programming concepts to Java, making code more concise and expressive.

Lambda Syntax

Lambda expressions are defined with a parameter list, an arrow -> , and a body.

// Traditional approach Runnable runnable = new Runnable() { public void run() { System.out.println("Hello, World!"); } }; // Lambda expression Runnable lambdaRunnable = () -> System.out.println("Hello, World!");

Functional Interfaces

Functional interfaces define a single abstract method and are crucial for using lambda expressions.

Java Functional Programming

Functional programming (FP) principles emphasize immutability, pure functions, and higher-order functions.

Functional Concepts

Immutability: Avoid changing data after creation.
Pure Functions: Functions with no side effects.
Higher-Order Functions: Functions that accept or return other functions.

Benefits and Use Cases

FP can lead to more concise, predictable, and maintainable code. It's particularly useful in parallel and asynchronous programming.

Tricky Java Coding Exercises

Now, it's time to put your Java skills to the test with tricky coding exercises. These exercises will help you develop problem-solving abilities and apply your knowledge effectively.

Problem-Solving Approach

Before jumping into coding challenges, let's establish a problem-solving approach that will serve as your foundation.

Algorithm Design

Understand the Problem: Carefully read and comprehend the problem statement.
Plan Your Approach: Devise a strategy or algorithm to solve the problem step by step.
Implement Your Solution: Write clear and concise code based on your plan.
Test and Debug: Test your code with various inputs and debug any issues.
Optimize: Analyze your code for efficiency and make improvements if needed.

Coding Challenges and Solutions

Now, let's explore some common Java coding challenges and their solutions. These examples will help you apply your problem-solving skills and Java knowledge effectively.

Example: Finding the Maximum Number in an Array

Problem: Write a Java program to find the maximum number in an array.

public class MaxInArray { public static int findMax(int[] arr) { if (arr == null || arr.length == 0) { throw new IllegalArgumentException("Array is empty or null."); } int max = arr[0]; for (int num : arr) { if (num > max) { max = num; } } return max; } public static void main(String[] args) { int[] numbers = { 23, 45, 12, 67, 8, 56 }; int maxNumber = findMax(numbers); System.out.println("The maximum number is: " + maxNumber); } }

In this example, we define a findMax method that iterates through the array and keeps track of the maximum value. The main method demonstrates how to use this method.

Example: Reversing a String

Problem: Write a Java program to reverse a string.

public class ReverseString { public static String reverse(String input) { if (input == null) { throw new IllegalArgumentException("Input string is null."); } StringBuilder reversed = new StringBuilder(); for (int i = input.length() - 1; i >= 0; i--) { reversed.append(input.charAt(i)); } return reversed.toString(); } public static void main(String[] args) { String original = "Hello, World!"; String reversedString = reverse(original); System.out.println("Reversed string: " + reversedString); } }

In this example, the reverse method takes an input string and builds a reversed version of it using a StringBuilder .

Time and Space Complexity Analysis

When solving coding exercises, it's essential to analyze the time and space complexity of your solutions.

Time Complexity: Assess how the runtime of your algorithm scales with input size (e.g., O(n), O(n^2), etc.).
Space Complexity: Evaluate the amount of memory your algorithm uses relative to the input size.

By understanding these complexities, you can optimize your code and choose the most efficient solutions for different scenarios.

As you tackle more coding exercises and analyze their complexities, you'll become better equipped to solve challenging Java interview questions.

How to Ace Tricky Java Interviews?

Congratulations on mastering the core Java concepts, exploring advanced topics, and honing your coding skills! Now, let's focus on essential tips and strategies to ensure you shine in those tricky Java interviews.

Interview Strategies

Interview success isn't just about what you know; it's also about how you present yourself and approach the interview.

Pre-Interview Preparation

Research the Company: Understand the company's products, culture, and values.
Review Your Resume: Be ready to discuss your past experiences and projects.
Know Your Strengths and Weaknesses: Prepare to highlight your strengths and show how you've worked on your weaknesses.

During the Interview

Active Listening: Pay close attention to the interviewer's questions and instructions.
Ask Clarifying Questions: If a question is unclear, don't hesitate to seek clarification.
Think Aloud: When solving problems, share your thought process with the interviewer.
Stay Calm: If you encounter a challenging question, stay composed and don't rush.
Time Management: Allocate your time wisely to ensure you address all parts of the interview.

Communication Skills

Effective communication is vital during interviews to convey your ideas clearly and confidently.

Clear Communication

Use Simple Language: Avoid jargon and use plain, understandable language.
Structure Your Answers: Organize your responses logically with clear introductions and conclusions.
Avoid Rambling: Be concise and to the point.

Asking Questions

Prepare Questions: Have insightful questions ready to ask the interviewer.
Show Interest: Ask questions that demonstrate your genuine interest in the role and company.

Handling Behavioral Questions

Behavioral questions assess your past experiences and how you've handled specific situations.

STAR Technique

Situation: Describe the context and situation you faced.
Task: Explain the task or challenge you had to address.
Action: Detail the actions you took to resolve the issue.
Result: Summarize the positive outcome and what you learned.

Answering Ethical Dilemmas

Prepare for ethical and moral questions by considering your values and ethical principles. Be honest and transparent about how you would handle such situations.

Handling Whiteboard Coding

Whiteboard coding can be daunting, but with practice and the right approach, you can excel.

Understand the Problem: Clarify the problem statement with the interviewer.
Pseudocode: Outline your solution before writing actual code.
Discuss Complexity: Mention the time and space complexity of your solution.
Practice: Practice whiteboard coding regularly to build confidence.

Post-Interview Follow-Up

Don't forget the importance of post-interview etiquette.

Thank-You Notes

Send a Thank-You Email: Express your gratitude for the interview opportunity.
Reiterate Your Interest: Reiterate your enthusiasm for the role and the company.

Feedback Request

Ask for Feedback: Politely request feedback on your interview performance.
Learn and Improve: Use feedback to enhance your skills for future interviews.

By following these tips and strategies, you'll not only demonstrate your technical prowess but also showcase your professionalism and interpersonal skills, setting you on the path to success in your tricky Java interviews.

Navigating tricky Java interview questions is a journey that demands preparation, practice, and a passion for learning. By mastering core Java concepts, embracing advanced topics, and honing your coding skills, you've equipped yourself with the tools needed to excel in challenging interviews.

Remember, interview success isn't just about what you know—it's about how you present yourself, communicate effectively, and handle pressure. With the right strategies and a commitment to continuous improvement, you're well-prepared to tackle any tricky Java interview that comes your way.

How critical thinking can help you learn to code

Become a Software Engineer in Months, Not Years

From your first line of code, to your first day on the job — Educative has you covered. Join 2M+ developers learning in-demand programming skills.

Experienced programmers frequently say that being able to problem-solve effectively is one of the most important skills they use in their work. In programming as in life, problems don’t usually have magical solutions. Solving a coding problem often means looking at the problem from multiple perspectives, breaking it down into its constituent parts, and then considering (and maybe trying) several approaches to addressing it.

In short, being a good problem-solver requires critical thinking .

Today, we’ll discuss what critical thinking is, why it’s important, and how it can make you a better programmer.

We’ll cover :

What is critical thinking?

Why is critical thinking important in programming, how you can start thinking more critically, apply critical thinking today.

Learn to code today. Try one of our courses on programming fundamentals: Learn to Code: Python for Absolute Beginners Learn to Code: C++ for Absolute Beginners Learn to Code: C# for Absolute Beginners Learn to Code: Java for Absolute Beginners Learn to Code: JavaScript for Absolute Beginners Learn to Code: Ruby for Absolute Beginners

Learn in-demand tech skills in half the time

Mock Interview

Skill Paths

Assessments

Learn to Code

Tech Interview Prep

Generative AI

Data Science

Machine Learning

GitHub Students Scholarship

Early Access Courses

For Individuals

Try for Free

Gift a Subscription

Become an Author

Become an Affiliate

Earn Referral Credits

Cheatsheets

Frequently Asked Questions

Cookie Policy

Business Terms of Service

Data Processing Agreement

Selected Reading
UPSC IAS Exams Notes
Developer's Best Practices
Questions and Answers
Effective Resume Writing
HR Interview Questions
Computer Glossary

Critical Thinking Tutorial

Critical Thinking is the technique of analyzing thoughts and presenting them for positive criticism so that the final ideas are feasible and viable. This helps in coming up with clear, reasoned arguments. In business world, Critical Thinking is defined as a set of policies that are implemented and practiced to prevent any employee from exhibiting deviant behaviors. It helps in addressing any problem at its nascent stage so that it can be prevented from spiraling out of control. This tutorial covers all the important points that readers should keep in mind while taking important decisions.

This tutorial is for designed primarily for those professionals who are looking for guidance in handling different kinds of co-workers at the workplace. This tutorial will guide you in getting prepared for any adverse situation in the office.

Prerequisites

Before proceeding with this tutorial, you are expected to have a calm mindset and be open to exploring the suggestions mentioned here.

To Continue Learning Please Login

Hire experienced tutors to satisfy your "write essay for me" requests.

Enjoy free originality reports, 24/7 support, and unlimited edits for 30 days after completion.

Our Team of Professional Essay Writers

As we are an honest and well-paying essay writer service, writers come flying our way. Nonetheless, in the writers' community, we are known for our strict selection process. You as a client can be sure that you will be working with the best paper writer in the game no matter your subject or the difficulty of the task as all our writers go through testing and have their degrees checked. Only 3% of all applicants are accepted to work with us and even these 3% have a training program and a two-month trial period ahead. We value our reputation and only hire true experts with years of experience in academic writing behind their backs. Nonetheless, being a professional writers service has its challenges. For example, as our employer expectations are high, not all writers can handle the challenge of creating zero-plagiarism essay writing content in a short time frame, so as leading writing services we must keep everything in control.

Finished Papers

a guide to programming in java critical thinking answers

Customer Reviews

How much does an essay cost?

Starting your search for an agency, you need to carefully study the services of each option. There are a lot of specialists in this area, so prices vary in a wide range. But you need to remember that the quality of work directly depends on the cost. Decide immediately what is more important to you - financial savings or the result.

Companies always indicate how much 1000 characters of text costs, so that the client understands what price to expect and whether it is worth continuing to cooperate.

At Essayswriting, it all depends on the timeline you put in it. Professional authors can write an essay in 3 hours, if there is a certain volume, but it must be borne in mind that with such a service the price will be the highest. The cheapest estimate is the work that needs to be done in 14 days. Then 275 words will cost you $ 10, while 3 hours will cost you $ 50. Please, take into consideration that VAT tax is totally included in the mentioned prices. The tax will be charged only from EU customers.

When choosing an agency, try to pay more attention to the level of professionalism, and then evaluate the high cost of work.

Jalan Zamrud Raya Ruko Permata Puri 1 Blok L1 No. 10, Kecamatan Cimanggis, Kota Depok, Jawa Barat 16452

The narration in my narrative work needs to be smooth and appealing to the readers while writing my essay. Our writers enhance the elements in the writing as per the demand of such a narrative piece that interests the readers and urges them to read along with the entire writing.

What if I’m unsatisfied with an essay your paper service delivers?

Professional essay writing services

Johan Wideroos