101 Java Interview Questions for Freshers

The tech world is incomplete without Java, which is why Java is one of the most popular programming languages worldwide. It is known for its versatility, portability, and wide range of applications. Because of its features and performance, Java is the most used language in top companies such as Google, Facebook, Uber, Twitter, Airbnb, Netflix, Instagram, Spotify, LinkedIn, Canva, Amazon, and many more. This list is endless; insiders say the market is huge, and the tech industry is always looking to hire experts in Java.

So, if you want to prepare for an interview for a Java developer, a freelance project, or a job, these random Java interview questions for freshers will help you with the knowledge you need to impress.

Here are 101 Essential Java Interview Questions For Freshers that the interviewer can ask a developer to evaluate their language understanding.

1. What is Java?
2. What are the features of Java?
3. What is JVM?
4. What is the difference between JDK, JRE, and JVM?
5. What are the differences between C++ and Java?
6. List the features of Java programming language.
7. What is the difference between a class and an object?
8. What is object-oriented programming?
9. What are the four principles of OOP?
10. How to find sum of all digits of a number in Java?
11. What do you understand by Java virtual machine?
12. How many types of memory areas are allocated by JVM?
13. What is JIT compiler?
14. Why Java is platform independent?
15. Why Java is not 100% Object-oriented?
16. What are wrapper classes in Java?
17. What is inheritance?
18. What is encapsulation?
19. What is polymorphism?
20. What is abstraction?
21. What are access modifiers?
22. What are static variables and methods?
23. How to perform matrix operations in Java?
24. What are the final variables and methods?
25. What is a constructor in Java?
26. What are the different types of variables in Java?
27. What is an array?
28. What are control structures in Java?
29. What is exception handling?
30. Can the main method be Overloaded?
31. What are the different types of exceptions in Java?
32. How to find largest number less than a given number and without a given digit?
33. What is the difference between a HashSet and a TreeSet?
34. How can you implement a Stack using an Array?
35. What is the difference between a shallow copy and a deep copy in Java?
36. How do you reverse a linked list in Java?
37. Write a Java program to reverse a string.
38. How to check whether given number is binary or not?
39. What is the difference between a String, StringBuilder, and StringBuffer in Java?
40. What is a binary search tree? How can you implement one in Java?
41. What is the difference between an abstract class and an interface in Java?
42. How do you handle multiple exceptions in Java?
43. How do you implement a merge sort algorithm in Java?
44. Provide an example of Polymorphism.
45. How to check whether one string is a rotation of another in Java?
46. What is a lambda expression in Java? Provide an example.
47. How does Garbage Collection prevent a Java application from going out of memory?
48. What’s the difference between a ClassNotFoundException and NoClassDefFoundError?
49. How to find intersection of two arrays in Java?
50. Can an enum be extended?
51. When do you use volatile variables?
52. What is the difference between a private and a protected method in Java?
53. How do you implement a bubble sort algorithm in Java?
54. What is the difference between a while loop and a do-while loop in Java?
55. How do you implement a binary search algorithm in Java?
56. What is a thread in Java? Provide an example of how to create a thread.
57. Decimal To Binary, Decimal To Octal And Decimal To HexaDecimal In Java
58. What is the difference between a static and non-static variable in Java?
59. Java program to print all sub strings of a string.
60. How to separate zeros from non-zeros in an array?
61. What is a deadlock in Java? How can you prevent it?
62. What is an interface in Java? Provide an example.
63. How to sort array elements by frequency in Java? 
64. Pronic number program in Java
65. How do you implement a quick sort algorithm in Java?
66. Java program to print common characters between two strings in alphabetical order. 
67. How to merge two sorted arrays in Java?
68. Write a Java program to swap two string variables without using third or temp variable?
69. Why is synchronization necessary? Explain with the help of a relevant example.
70. How to merge two unsorted arrays in sorted order in Java?
71. How do you find longest substring without repeating characters in a string?
72. Write a Java program to append text to a file?
73. Roman equivalent of a decimal number
74. Disarium Number Program In Java
75. Text File Modification Program
76. Magic number program in Java
77. What is the difference between final, finalize and finally?
78. How to check whether user input is number or not in Java?
79. How to read and write images in Java?
80. Difference between two dates in Java
81. Symmetric Matrix Program In Java
82. How to list all files in a directory in Java?
83. Pattern Programs In Java
84. When can you use the super keyword?
85. What makes a HashSet different from a TreeSet?
86. What are the uses of synchronized keywords?
87. What is an infinite loop in Java? Explain with an example.
88. Bubble Sort Algorithm In Java
89. What is singleton class in Java and how can we make a class singleton?
90. What is the difference between equals() and == in Java?
91. What are the differences between HashMap and HashTable in Java?
92. How does HashMap work in Java?
93. What are the differences between wait() and sleep()?
94. What are the uses of synchronized keywords?
95. What is the importance of reflection in Java?
96. How to not allow serialization of attributes of a class in Java?
97. Explain the term “Double Brace Initialization” in Java?
98. Why is it said that the length() method of String class doesn’t return accurate results?
99. What are the differences between Heap and Stack Memory in Java?
100. Why pointers are not used in Java?
101. What is Object Oriented Programming?