一个类可以实现多个有相同方法的接口

public class Computer implements Device, Action{
public void doIt() { System.out.println("");}
}
abstract class Phone1 extends Computer { }
abstract class Phone2 extends Computer{
public void doIt(int x) { }
}
class Phone3 extends Computer implements Device{
public void doStuff() { }
}
interface Device {
public void doIt();
String ACTION="DEVICE";
}

interface Action {
public void doIt();
String ACTION = "TEST1";
}