设计模式-状态模式

Posted 2022-07-14 bosslv

1. 定义
   允许对象在内部状态改变时改变它的行为，对象看起来好像修改了它的类。
2. 说明
   将状态封装成为独立的类，并将动作委托到代表当前状态的对象。

3. 代码实例

   /**
    * 场景描述：开关电脑状态机。当关闭状态时，按下按钮到开启状态。当开启状态时，按下按钮到关闭状态。
    */
   
   /**
    * 状态封装动作行为
    */
   interface State 
       void press();
   
   
   /**
    * 开启状态下的行为
    */
   class OpenState implements State 
       private Computer computer;
   
       public OpenState(Computer computer) 
           this.computer = computer;
       
   
       @Override
       public void press() 
           System.out.println("关闭电脑");
           computer.setCurrentState(computer.getCloseState());
       
   
   
   /**
    * 关闭状态下的行为
    */
   class CloseState implements State 
   
       private Computer computer;
   
       public CloseState(Computer computer) 
           this.computer = computer;
       
       @Override
       public void press() 
           System.out.println("打开电脑");
           computer.setCurrentState(computer.getOpenState());
       
   
   
   
   class Computer
   
       private State openState;
       private State closeState;
   
       private State currentState;
   
       public Computer() 
           openState = new OpenState(this);
           closeState = new CloseState(this);
   
           currentState = closeState;
       
   
       public void press() 
           currentState.press();
       
   
       /* 以下为辅助方法 */
   
       public void setCurrentState(State currentState) 
           this.currentState = currentState;
       
   
       public State getCloseState() 
           return closeState;
       
   
       public State getOpenState() 
           return openState;
       
   
       // 测试
       public static void main(String[] args) 
           Computer computer = new Computer();
           computer.press();
           computer.press();
           computer.press();
           computer.press();