In java, how can we override the default method?

The default method in Java may be a method in java which are defined inside the interface with the keyword default is understood because of the default method. it's a kind of non-abstract method.

This method is capable of adding backward capability in order that the old interface can grasp the lambda expression capability.

Java Interface Default method is additionally referred to as Defender Method or virtual extension method.

Interfaces could have only abstract methods before Java 8. The classes separately provide implementation to those methods. So, if a replacement method is to be added to an interface, then its implementation code has got to be provided within the class implementing an equivalent interface. For overcoming this issue, Java 8 introduced the concept of default methods that allow the interfaces to possess methods with implementation without affecting the classes that implement the interface.

In java, how can we override the default method?

It is not mandatory to override the default method in Java.

If we are using just one interface during a Program then at a time we are using only one default method and at that point, Overriding isn't required as shown within the below program:

JAVA

// Creating Interface
interface GfG{

public default void display() {
	System.out.println("GEEKSFORGEEKS");
}
}

// Main Class With Implementation Of Interface
public class InterfaceExample implements GfG{
public static void main(String args[]) {
	InterfaceExample obj = new InterfaceExample();
	
	// Calling Interface
	obj.display();
}
}

Output

GEEKSFORGEEKS

But when quite two Interfaces are used and both act as parent class then at that point Overriding of the Default Method is required. If we are using quite one interface and in both interfaces, if both interfaces have an equivalent name and same structure. So at that point, one must override either one both the default method otherwise it'll end in a mistake.

Case 1: When Two Interfaces are not overridden

Java

// Java program to demonstrate the case when
// two interfaces are not overridden

// Creating Interface One
interface GfG{
public default void display() {
	System.out.println("GEEKSFORGEEKS");
}
}

// Creating Interface Two
interface gfg{

public default void display() {
	System.out.println("geeksforgeeks");
}
}

// Interfaces are not Overidden
public class InterfaceExample implements GfG,gfg {
public static void main(String args[])
{
	InterfaceExample obj = new InterfaceExample();
	obj.display();
}
}

Output:

InterfaceExample.java:18: error: types GfG and gfg are incompatible;
public class InterfaceExample implements GfG,gfg {
       ^
  class InterfaceExample inherits unrelated defaults for display() from types GfG and gfg
1 error

Case 2: When Two Interfaces are Overridden

Java

// Java program to demonstrate the case
// when two interfaces are overridden

// Creating Interface One
interface GfG{
public default void display()
{
	System.out.println("GEEKSFORGEEKS");
}
}

// Creating Interface Two
interface gfg{

public default void display()
{
	System.out.println("geeksforgeeks");
}
}

public class InterfaceExample implements GfG,gfg {

// Interfaces are Overrided
public void display() {
	
	GfG.super.display();
	
	gfg.super.display();
}

public static void main(String args[]) {
	InterfaceExample obj = new InterfaceExample();
	obj.display();
}
}

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