Java Interview Questions

Java Interview Questions

Java interview questions covering core Java, OOP, multithreading, and collections.

36 Topics Beginner to Advanced 3+ Hours

1

Java Basics – What is Java?

2

What is the difference between JVM, JRE, and JDK?

3

What are the OOP concepts in Java?

4

Why is the main method static in Java?

5

What are the different data types in Java?

6

What is the difference between a class and an object in Java?

7

What is Method Overloading and Method Overriding in Java?

8

What is the Difference Between Abstract Class and Interface in Java?

9

What is the Constructor in Java and What Are Its Types?

10

What are the Access Modifiers in Java? (Public, Private, Protected, Default)

11

What is the this Keyword in Java?

12

What is the super Keyword in Java?

13

What is the static Keyword in Java? (Variables, Methods, Block)

14

What is the final Keyword in Java?

15

What is Exception Handling in Java? (Try, Catch, Finally, Throw, Throws)

16

What are Checked and Unchecked Exceptions in Java?

17

What is the Difference Between Error and Exception in Java?

18

What are Multithreading and Concurrency in Java?

19

What is the Java Collections Framework? (List, Set, Map)

20

What is the Difference Between ArrayList and LinkedList in Java?

21

What is the Difference Between HashSet and TreeSet in Java?

22

What is the Difference Between HashMap and TreeMap in Java?

23

What is the Difference Between HashMap and Hashtable in Java?

24

How Does HashMap Work Internally in Java?

25

What is the Difference Between Iterator and ListIterator in Java?

26

What is the Difference Between Comparable and Comparator in Java?

27

What is the String Pool in Java?

28

What is the Difference Between String, StringBuilder, and StringBuffer?

29

What is Garbage Collection in Java and How Does It Work?

30

What is the Difference Between final, finally, and finalize in Java?

31

What is a Lambda Expression in Java 8?

32

What is the Stream API in Java 8?

33

What are Optional Class and Its Benefits in Java 8?

34

What is the Difference Between Java 8 and Java 11?

35

What are the Key Features of Java 17 (LTS)?

36

What is the Record Class in Java 14/17?

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