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What are Default Methods in Java 8?
Interface in Java is similar to class but, it contains only abstract methods and fields which are final and static.
In a separate class you need to implement this interface and provide body for all its abstract methods.
Example
interface MyInterface{
public void demo();
}
public class InterfaceExample implements MyInterface{
public void demo() {
System.out.println("This is the implementation of the demo method");
}
public static void main(String args[]) {
new InterfaceExample().demo();
}
}Output
This is the implementation of the demo method
If a new method is added to an interface, you need to provide body for this method in all the classes implementing its interface
Default method
From JSE8 Default methods are introduced in Java. Since then, you can write a default implementation to a particular method in an interface. If you do so, there is no need to implement these (default methods) in the classes that already implement this interface.
A default method is also known as defender method or virtual extension method. You can define a default method using the default keyword as −
default void display() {
System.out.println("This is a default method");
}Note − All the methods of an interface are public therefore there is no need to use public before it explicitly.
Example
Following Java Example demonstrates the usage of the default method in Java.
interface sampleInterface{
public void demo();
default void display() {
System.out.println("This is a default method");
}
}
public class DefaultMethodExample implements sampleInterface{
public void demo() {
System.out.println("This is the implementation of the demo method");
}
public static void main(String args[]) {
DefaultMethodExample obj = new DefaultMethodExample();
obj.demo();
obj.display();
}
}Output
This is the implementation of the demo method This is a default method
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