Commonly Asked Java Programming Interview Questions

Interviews always create some tensed situation and to make you feel easy about them, here we share some commonly asked java interview questions for experienced. And also shared the best suitable answers from the internet sources for java programming interview questions.

Some common Java interview questions with answers:

1) What is Overload or Override static methods in java?

Overriding: This is associated with run-time polymorphism. A subclass gives a specific implementation of a method in super class at runtime.

Overloading: This is associated with compile-time polymorphism. This permits different methods to have the same name, but various signatures, mainly number of input parameters and type of input parameters.

2) Can you override static methods in java?

No. You cannot override static methods in Java.

3) Why the is main method static in java?

This is because otherwise there will appear ambiguity.

4) What is the outcome if you remove static modifier from the main method?

The program compiles successfully. But at runtime, there is an error, “NoSuchMethodError”.

5) What is “this” keyword in java?

In a method of an instance, “this” refers to the current object, the object whose method or constructor is being called.

6) Which class is a super class for every class?

Object class

7) How to overload main () method?

The main method is no extra-terrestrial method. The matter about main() is like any other method & can be overloaded likewise, JVM always looks for method signature to launch the program.

8) What is object cloning?

This is to develop an exact copy of the original object. If the class requires to support cloning, it must implement java.lang.

9) Why method overloading impossible by changing return type in java?

In C++ and Java, functions can’t be overloaded if they vary only in return type. The number of arguments, Types & Sequence of arguments is parameters to yield the unique mangled name for every function.

10) How to override private methods in Java?

A private method can’t be overridden for not being visible from any other class.

11) What is blank final variable?

A final variable could be given on a value only once; it can be given either in the declaration or later.

A blank final variable in Java is a final variable which is not initialized during declaration.

12) Define “super” keyword in java?

This is a reference variable which refers to parent class objects. When you develop an instance of a subclass, an instance of the parent class is developed.

13) How to use java super Keyword:

  • super is used to mention immediate parent instance variable

  • super is used to summon parent class method

  • Super () is used to summon immediate parent constructor

14) Define a static variable in Java?

The static keyword is utilized for managing memory. You can use java static keyword with variables, methods, blocks and nested class. The static can be:

Variable

Method

Block

Nested class

15) Differentiate between HashMap and HashTable in Java.

1. HashMap is not synchronized.

2. HashMap permits 1 null key and multiple null values while Hashtable doesn’t permit any null key or value.

3. HashMap is preferred over HashTable if thread synchronization is not required.

16) How are Java objects stored in memory?

In Java, all objects are kept on Heap. While in C++ objects are allocated memory either on Stack or on Heap. In Java, when a variable is declared of a class type, just a reference is created. To allocate memory to an object, you must use new ().

With this, we conclude. Hope the above java programming interview questions and answers would help you. And keep looking into this space by career advice for more career guidance tips, news, and updates.

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