Top Java Interview Questions And Answer 2025

1. What is Java?
– Java is a high level object orientated programming language that is platform independent and convenient to develop.

2. Give a description of the core fundamentals of Java.
– Platform independence, object-oriented, support for multithreading, automatic memory management, and strong exception-handling mechanism.

3. Outline the differences between JDK, JRE, and JVM.
– JDK is for developing, JRE for running, and JVM is the runtime environment.

4. What does the ‘static’ keyword mean in Java? listed Item:
– “static” refers to variables or methods that are owned by the class, instead of instances. This is a unique characteristic of the class and is shared amongst all instances of the class.

5. Discuss the phenomenon of method overloading.
– Method overloading makes it possible to provide a class with methods of identical names along with differing parameters, improving programmability and clearness.

6. What is Java’s approach to multiple inheritance?
– Java obtains multiple inheritance via interfaces, and a class can inherit many interfaces.

7. What is the essence of the “finalize” method?
– The garbage collector calls “finalize” method before object is reclaimed. It allows for cleanup operations.

8. What is the difference between “==” and “.equals()” in Java?
– “==” performs comparison of object references, whereas “.equals()” compare to objects themselves.

9. Explain the Java Collection Framework.
– Java Collection Framework is a group of classes and interfaces that offer implementations used by a wide variety of data structures like lists, sets, and maps.

10. What is the disparity between an abstract class and an interface?
– Abstract classes can have abstract as well as concrete methods while interfaces can only have abstract methods. While a class can inherit from multiples of interface, a single abstract class only.

11. So, how does Java’s handling of exceptions?
– Exception handling in Java involves the use of try, catch, and finally blocks. It is composed of a “try” block with the code that may trigger an exception followed by a “catch” handling the exception and a “finally” which executes regardless of whether an exception is caught.

12. The meaning of “transient” in Java.
– A “transient” keyword marks a variable which is not to be serially transferred during object serialization.

13. What does the “super” keyword means in Java?
– In a subclass, “super” refers to the members (methods, fields or constructor)of the superclass.

14. Discuss about polymorphism in Java.
– This feature enables the same method to work on objects belonging to entirely unrelated classes, thus promoting the flexibility and reusability of the code.

15. How does Java support multithreading?
– Multithreading is supported by Java through the `Thread` class and the `Runnable` interface for concurrent executions of different threads.

16. What do you use java’s “this” keyword for?
– This helps to differentiate between instance variables and local variables using the “this” keyword to refer to the current instance of the class.