interface Data1 {
    int a = 1;   
    int b = 2;   
    int calc1(); 
    int calc2(); 
}

interface Data2 extends Data1 {
    int c = 3;
    int calc3();
}

interface Data3 {
    int d = 4;
    int calc4();
}

class DataA implements Data1 {
    public int calc1() { return a; }
    public int calc2() { return b; }
}

class DataB extends DataA implements Data2, Data3 {
    public int calc3() { return c; }
    public int calc4() { return d; }
}

public class InterfaceFun2 {
    public static void main(String[] args) {

	DataA x = new DataB();

	// What happens if you use a ref type that doesn't specify 
	// at least one method that the object uses?
	// At compile time, Java checks method names with static binding,
	// so the following won't work because calc3 and calc4 aren't in DataA:

	//	System.out.println(x.calc1()+""+x.calc2()+""+
	//                         x.calc3()+""+x.calc4());

	// The following *does* work because the calc1 method is in DataA
	// and none of the other methods are inspected:

	System.out.println(x.calc1());
	
    }
}

// output: 1