[JAVA] Default And Static Method

Table of contents

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Overview

In this article, We will learn default method and static method in an interface in java 8 new features.

Before Java 1.7 we can declare only abstract methods in an Interface.

However from Java 1.8 onwards we can write concrete methods also in an Interface.

In Interface concrete methods should be either “default” or “static” only.

What is Default Method ?

The Default Method is a feature of Interfaces in Java 8. Methods that are defined inside the interface and tag with default are known as default methods.

The main advantage of default methods is without effecting implementation classes we can add new functionality to the interface.

One of the major reason for introducing default methods in interfaces is to enhance the Collections API in Java 8 to support lambda expressions.

Syntax of default methods:

Let’s understand the syntax of default methods through an example,

**Now we will create a class that implements an interface.**

Output:

In the following example, MyInterface is a functional interface that contains a default and an abstract method. So the concept of default method are use to define a method with default implementation. We can override default method also to provide more specific implementation for the method.

A Few Important Points for Default Methods

We can inherit the default method.
Redefine the default method (equivalent to overriding).

What is Static Method ?

From Java 8 we can write static methods also in an interface. Static methods are similar to default methods but the only difference is that you can’t override static methods.

Syntax of Static methods:

Now we understand the syntax of static methods through an example,

Now we will create a class which implements MyInterface interface.

Output

A Few Important Points for Static Methods

Static methods in Java are resolve at compile time. Method overriding is a part of Runtime Polymorphism.
Static methods can’t be overridden.
Abstract methods can’t be static.
static methods can’t use this or super keywords.