命令模式

命令模式对简单的调用关系进行解耦，再大多数情况下我们可以使用直接调用的方式来做，但是如果调用比较繁琐，那么使用命令模式不失为一个好选择

这里举一个超级马里奥移动的例子来讲解命令模式

超级马里奥的动作类

public class Mario {
    public void toLeft() {
        System.out.println("向左移");
    }

    public void toRight() {
        System.out.println("向右移");
    }

    public void toJump() {
        System.out.println("跳跃");
    }
}

定义执行方法接口

public interface Command {
    void execute();
}

定义具体命令类

1. 跳命令

   public class JumpCommand implements Command {
       private Mario mario;
       public JumpCommand(Mario mario) {
           this.mario = mario;
       }
       @Override
       public void execute() {
           mario.toJump();
       }
   }

2. 左移命令

   public class LeftCommand implements Command {
       private Mario mario;
       public LeftCommand(Mario mario) {
           this.mario = mario;
       }
       @Override
       public void execute() {
           mario.toLeft();
       }
   }

3. 右移命令

   public class RightCommand implements Command {
       private Mario mario;
       public RightCommand(Mario mario) {
           this.mario = mario;
       }
       @Override
       public void execute() {
           mario.toRight();
       }
   }

命令的包装：按钮类

public class Button {
    private JumpCommand jumpCommand;
    private LeftCommand leftCommand;
    private RightCommand rightCommand;

    public void setJumpCommand(JumpCommand jumpCommand) {
        this.jumpCommand = jumpCommand;
    }

    public void setLeftCommand(LeftCommand leftCommand) {
        this.leftCommand = leftCommand;
    }

    public void setRightCommand(RightCommand rightCommand) {
        this.rightCommand = rightCommand;
    }

    public void jump() {
        jumpCommand.execute();
    }

    public void left() {
        leftCommand.execute();
    }

    public void right() {
        rightCommand.execute();
    }
}

具体执行

public class Main {
    public static void main(String[] args) {
        Mario mario = new Mario();
        LeftCommand leftCommand = new LeftCommand(mario);
        RightCommand rightCommand = new RightCommand(mario);
        JumpCommand jumpCommand = new JumpCommand(mario);
        Button button = new Button();
        button.setJumpCommand(jumpCommand);
        button.setLeftCommand(leftCommand);
        button.setRightCommand(rightCommand);
        button.jump();
        button.left();
        button.right();
    }
}

命令类可以在相当程度上实现调用逻辑的解耦，但是像大家看到的一样，需要多出很多的类，但是这样设计模式的原则：对修改关闭，对扩展开放，才能提到体现