桥接模式

public interface  EndPlace {
     void to();
}

public class EndPlaceA implements  EndPlace {
    @Override
    public void to() {
        System.out.println("去A");
    }
}

public class EndPlaceB implements EndPlace {
    @Override
    public void to() {
        System.out.println("去B");
    }
}

public abstract class StartPlace {
    EndPlace endPlace;
    protected  StartPlace(EndPlace endPlace){
        this.endPlace = endPlace;
    }
    abstract  void from();
}

public class StartPlaceA extends StartPlace {
    public StartPlaceA(EndPlace endPlace){
        super(endPlace);
    }
    @Override
    void from() {
        System.out.println("来自A");
    }
}

public class StartPlaceB extends StartPlace {
    protected StartPlaceB(EndPlace endPlace) {
        super(endPlace);
    }
    @Override
    void from() {
        System.out.println("来自B");
    }
}

public class Client {
    public static void main(String[] args){
        StartPlace sa  = new StartPlaceA(new EndPlaceB());
        sa.from();
        sa.endPlace.to();
        sa = new StartPlaceA(new EndPlaceA());
        sa.from();
        sa.endPlace.to();

        StartPlace sb  = new StartPlaceB(new EndPlaceB());
        sb.from();
        sb.endPlace.to();
        sb = new StartPlaceB(new EndPlaceA());
        sb.from();
        sb.endPlace.to();
    }
}