首先一個(gè)請(qǐng)求對(duì)象笛洛，暫時(shí)命名為invoke，發(fā)出請(qǐng)求咐蚯，而這個(gè)請(qǐng)求用Command來(lái)表示球碉，receiver表示接受者，收到消息可以執(zhí)行仓蛆，代碼表示如下

public class Invoker {
    //長(zhǎng)官發(fā)出命令
    private Command command;

    public Invoker(Command command) {
        this.command = command;
    }
}

public interface  Command {
    //命令對(duì)象本體
     void execute();
}

public class Receiver {

    //執(zhí)行操作
    public  void doit(){
        System.err.println("do it.....");
    }
    //撤銷操作
    public  void undo(){
        System.err.println("undo it.....");
    }
}

命令模式睁冬，四個(gè)字可以看出依據(jù)命令來(lái)行事，命令是多個(gè)的,所以實(shí)現(xiàn)多個(gè)命令

public class OrderFruit implements Command{
    private Receiver receiver;
    @Override
    public void execute() {
        receiver.doit();
    }
}


public class OrderDrink implements Command{
    private Receiver receiver;
    @Override
    public void execute() {
        receiver.doit();
    }
}

上面命令的受體都是同一個(gè)對(duì)象看疙，改動(dòng)下不同的命令為不同受體豆拨，可以抽象一個(gè)類，在繼承或者實(shí)現(xiàn)能庆，其實(shí)本質(zhì)都沒(méi)有變化

//對(duì)Recriver 類進(jìn)行幻化
public class FruitReceiver {

    //執(zhí)行操作
    public  void orderFruit(){
        System.err.println("do it.....order fruit");
    }
    //撤銷操作
    public  void undo(){
        System.err.println("undo it..... cancal fruit");
    }
}

public class DrinkReceiver {

    //執(zhí)行操作
    public  void orderFruit(){
        System.err.println("do it.....order drink");
    }
    //撤銷操作
    public  void undo(){
        System.err.println("undo it..... cancal drink");
    }
}

相對(duì)的改變命令Command受體對(duì)象

public class OrderDrink implements Command{
    private DrinkReceiver receiver;
    @Override
    public void execute() {
        receiver.orderDrink();
    }
}

public class OrderFruit implements Command{
    private FruitReceiver receiver;


    @Override
    public void execute() {
        receiver.orderFruit();
    }
}

public class CancelFruit implements Command{
    private FruitReceiver receiver;

    public CancelFruit(FruitReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    public void execute() {
        receiver.undoFruit();
    }
}



public class CancelDrink implements Command{
    private DrinkReceiver receiver;

    public CancelDrink(DrinkReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    public void execute() {
        receiver.undoDrink();
    }
}

改造下發(fā)請(qǐng)求的人施禾，網(wǎng)上很多寫法，能發(fā)出命令就可以了

ublic class Invoker {
    //命令收集者
    private List<Command> commands=new ArrayList<>();

    public void addCommand(Command command){
        commands.add(command);
    }

    public void execute(){
        //把命令記錄打一遍
        for (Command command : commands) {
            command.execute();
        }
    }
}

設(shè)置場(chǎng)景類驗(yàn)證

public class Client {
    public static void main(String[] args) {
        DrinkReceiver drinkReceiver = new DrinkReceiver();//賣水人
        FruitReceiver fruitReceiver = new FruitReceiver();//賣水果人

        Invoker invoker = new Invoker();//把命令收集起來(lái)執(zhí)行
        OrderDrink orderDrink = new OrderDrink(drinkReceiver);//買水
        OrderFruit orderFruit = new OrderFruit(fruitReceiver);//買水果
        invoker.addCommand(orderDrink);
        invoker.addCommand(orderFruit);
        //太貴了搁胆，我又不想買了
        CancelDrink cancelDrink = new CancelDrink(drinkReceiver);
        CancelFruit cancelFruit = new CancelFruit(fruitReceiver);
        invoker.addCommand(cancelDrink);
        invoker.addCommand(cancelFruit);

        invoker.execute();
    }
}