Interface

interface I1 {

void methodI1(); // public static by default
}

interface I2 extends I1 {

void methodI2(); // public static by default
}

class A1 {

public String methodA1() {
String strA1 = "I am in methodC1 of class A1";
return strA1;
}
public String toString() {
return "toString() method of class A1";
}
}

class B1 extends A1 implements I2 {

public void methodI1() {
System.out.println("I am in methodI1 of class B1");
}
public void methodI2() {
System.out.println("I am in methodI2 of class B1");
}
}

class C1 implements I2 {

public void methodI1() {
System.out.println("I am in methodI1 of class C1");
}
public void methodI2() {
System.out.println("I am in methodI2 of class C1");
}
}


abstract class D1 implements I2 {

public void methodI1() {
}

}

public class InterFaceEx {

public static void main(String[] args) {
I1 i1 = new B1();
i1.methodI1();
((I2) i1).methodI2();
I2 i2 = new B1();
i2.methodI1();
i2.methodI2();


String var2 = ((A1) i1).methodA1();
System.out.println("var2 : " + var2);
String var3 = ((B1) i1).methodA1();
System.out.println("var3 : " + var3);
String var4 = i1.toString();
System.out.println("var4 : " + var4);
String var5 = i2.toString();
System.out.println("var5 : " + var5);
I1 i3 = new C1();
String var6 = i3.toString();
System.out.println("var6 : " + var6);
Object o1 = new B1();

((I1) o1).methodI1();
((I2) o1).methodI1();
((B1) o1).methodI1();

}
}