Java interview questions and Answers

It is a prototype or user-defined blueprint that is used to create objects or data types. A class represents properties or methods that are common to objects of one type. All class objects possess the class properties.

It is the core unit of Object-Oriented Programming and represents real entities. As we know, a Java program creates objects that interact by invoking various methods.

An object consists of state, behavior, and identity.

The constructor is a method used to initialize an object. A normal java method has return type but the constructor does not have any explicit return type. It is called during the object creation time.

There is two type of Constructors - Default or no-arg Constructor, Parameterized Constructor.

It is a reference variable that refers to the current object. It can be used as follows:

• To refer instance variable of class
• To invoke class constructor
• Passed as an argument in method call
• Passed as an argument in the constructor call
• Used to return a class instance

It is the process when one class acquires the properties or methods or fields of another class. This process is used to arrange and manage information in hierarchical order. The class that inherits the properties is called subclass. The class whose properties get inherited is called superclass.

It is one of the features of object-oriented programming that allows the developers to perform one action in different ways. Developers often use Polymorphism in referencing a parent class to a child class object.

Method overriding is a feature in object-oriented programming that allows a child class to give a specific implementation method that is already given by its parent classes.

Method Overloading allows a class to have more than one methods of having the same name, but only if the argument lists are varying. This feature is similar to constructor overloading feature that allows more than one constructor to a class only if their argument lists are different.