命令模式

public class Receiver {
    public void extA()
    {
        System.out.println("Command excA!!");
    }
    public void extB()
    {
        System.out.println("Command excB!!");
    }
}

public abstract class Command {
    public Receiver rec=null;
    public void setRec(Receiver rec) 
    {
        this.rec=rec;
    }
    public abstract void exc();
}
public class CommandImpA extends Command {
    public void exc() {
        rec.extA();
    }
}
public class CommandImpB extends Command{
    public void exc() {
        rec.extB();
    }
}

public class Invoker {
    private ArrayList<Command> cmdList=new ArrayList<Command>();
    public void setCommand(Command cmd)
    {
        this.cmdList.add(cmd);
    }
    public void exc()
    {
        for(Command cmd:cmdList)
        {
            cmd.exc();
        }
    }
}

public static void main(String[] args) {
        Command cmdA=new CommandImpA();
        Command cmdB=new CommandImpB();
        cmdA.setRec(new Receiver());
        cmdB.setRec(new Receiver());
        Invoker ivk=new Invoker();
        ivk.setCommand(cmdA);
        ivk.setCommand(cmdB);
        ivk.setCommand(cmdB);
        ivk.setCommand(cmdA);
        ivk.setCommand(cmdA);
        ivk.setCommand(cmdA);
        ivk.exc();
    }