Definition-

Interface is a 100% abstract class.
– All methods in interface are public and abstract.
-All data members in interface are public, static and final.

– multiple inheritance is allowed in interfaces.

Note 1- class ‘implements’ interface

Note 2- interface ‘extends’ interface

Code samples are here

1- One class can implements multiple interfaces

a-

package intrfc;

public interface X {
void show();
}

b-

package intrfc;

public interface Y {
void display();
}

c-

package intrfc;

public class Z implements X,Y {
@Override
public void display() {
System.out.println("bye");
}

@Override
public void show() {
System.out.println("hi");
}
public static void main(String[] args) {
Z z=new Z();
z.show();
z.display();
}
}

 

2- Interface can extend other interface

a-

package intrfc;

public interface X1 {
void show();
}

b-

package intrfc;

public interface Y1 extends X1 {
void display();
}

c-

package intrfc;

public class Z1 implements Y1 {
@Override
public void display() {
System.out.println("bye");
}
@Override
public void show() {
System.out.println("hi");
}
public static void main(String[] args) {
Z1 z=new Z1();
z.show();
z.display();
}
}