状态模式的住店案例实战

状态模式可以有效的替换充满在程序中的 if else 语句：将不同条件下的行为封装在一个类里面，再给这些类一个统一的父类来约束他们。来看一下状态模式的角色组成：

1) 使用环境（Context）角色：客户程序是通过它来满足自己的需求。它定义了客户程序需要的接口；并且维护一个具体状态角色的实例，这个实例来决定当前的状态。

2) 状态（State）角色：定义一个接口以封装与使用环境角色的一个特定状态相关的行为。

3) 具体状态（Concrete State）角色：实现状态角色定义的接口。

类图如下，结构非常简单也与策略模式非常相似。

测试类，新开房3间，并设置状态

package com.cloud;

public class Test {
	public static void main(String[] args) {
		 //有3间房  
        Room[] rooms = new Room[2];  
        //初始化  
        for(int i = 0 ; i < rooms.length ; i++){  
            rooms[i] = new Room();  
        }  
        //第一间房  
        rooms[0].bookRoom();    //预订  
        rooms[0].checkInRoom();   //入住  
        rooms[0].bookRoom();    //预订  
        System.out.println(rooms[0]);  
        System.out.println("---------------------------");  
          
        //第二间房  
        rooms[1].checkInRoom();  
        rooms[1].bookRoom();  
        rooms[1].checkOutRoom();  
        rooms[1].bookRoom();  
        System.out.println(rooms[1]); 
	}
}

房间类定义如下

package com.cloud;

public class Room {
	/*  
     * 房间的三个状态  
     */  
    State freeTimeState;    //空闲状态  
    State checkInState;     //入住状态  
    State bookedState;      //预订状态  
  
    State state ;    
      
    public Room(){  
        freeTimeState = new FreeTimeState(this);  
        checkInState = new CheckInState(this);  
        bookedState = new BookedState(this);  
          
        state = freeTimeState ;  //初始状态为空闲  
    }  
      
    /**  
     * @desc 预订房间  
     * @return void  
     */  
    public void bookRoom(){  
        state.bookRoom();  
    }  
      
    /**  
     * @desc 退订房间  
     * @return void  
     */  
    public void unsubscribeRoom(){  
        state.unsubscribeRoom();  
    }  
      
    /**  
     * @desc 入住  
     * @return void  
     */  
    public void checkInRoom(){  
        state.checkInRoom();  
    }  
      
    /**  
     * @desc 退房  
     * @return void  
     */  
    public void checkOutRoom(){  
        state.checkOutRoom();  
    }  
  
    public String toString(){  
        return "该房间的状态是:"+getState().getClass().getName();  
    }  
      
    /*  
     * getter和setter方法  
     */  
      
    public State getFreeTimeState() {  
        return freeTimeState;  
    }  
  
    public void setFreeTimeState(State freeTimeState) {  
        this.freeTimeState = freeTimeState;  
    }  
  
    public State getCheckInState() {  
        return checkInState;  
    }  
  
    public void setCheckInState(State checkInState) {  
        this.checkInState = checkInState;  
    }  
  
    public State getBookedState() {  
        return bookedState;  
    }  
  
    public void setBookedState(State bookedState) {  
        this.bookedState = bookedState;  
    }  
  
    public State getState() {  
        return state;  
    }  
  
    public void setState(State state) {  
        this.state = state;  
    }  
  
}  

状态类定义如下

package com.cloud;

	public interface State {  
	    /**  
	     * @desc 预订房间  
	     * @return void  
	     */  
	    public void bookRoom();  
	      
	    /**  
	     * @desc 退订房间  
	     * @return void  
	     */  
	    public void unsubscribeRoom();  
	      
	    /**  
	     * @desc 入住  
	     * @return void  
	     */  
	    public void checkInRoom();  
	      
	    /**  
	     * @desc 退房  
	     * @return void  
	     */  
	    public void checkOutRoom();  
	      
	}  
	    

其他三个状态类如下

package com.cloud;

/**  
 * @project: design_state  
 * @author changyaobin 
 * @date 2017-8-24  
 * @Description: 入住状态房间只能退房 
 */  
public class BookedState implements State{
	  Room hotelManagement;  
      
	    public BookedState(Room hotelManagement) {  
	        this.hotelManagement = hotelManagement;  
	    }  
	  
	    public void bookRoom() {  
	        System.out.println("该房间已近给预定了...");  
	    }  
	  
	    public void checkInRoom() {  
	        System.out.println("入住成功...");   
	        hotelManagement.setState(hotelManagement.getCheckInState());         //状态变成入住  
	    }  
	  
	    public void checkOutRoom() {  
	        //不需要做操作  
	    }  
	  
	    public void unsubscribeRoom() {  
	        System.out.println("退订成功,欢迎下次光临...");  
	        hotelManagement.setState(hotelManagement.getFreeTimeState());   //变成空闲状态  
	    }  
}

public class CheckInState implements State {  
    Room hotelManagement;  
    public CheckInState(Room hotelManagement) {  
        this.hotelManagement = hotelManagement;  
    }  
  
    public void bookRoom() {  
        System.out.println("该房间已经入住了...");  
    }  
  
    public void checkInRoom() {  
        System.out.println("该房间已经入住了...");  
    }  
  
    public void checkOutRoom() {  
        System.out.println("退房成功....");  
        hotelManagement.setState(hotelManagement.getFreeTimeState());     //状态变成空闲  
    }  
  
    public void unsubscribeRoom() {  
        //不需要做操作  
    }  
  
}  
	public class FreeTimeState implements State {  
	      
	    Room hotelManagement;  
	      
	    public FreeTimeState(Room room){  
	        this.hotelManagement = room;  
	    }  
	      
	    public void bookRoom() {  
	        System.out.println("您已经成功预订了...");  
	        hotelManagement.setState(hotelManagement.getBookedState());   //状态变成已经预订  
	    }  
	    public void checkInRoom() {  
	        System.out.println("您已经成功入住了...");  
	        hotelManagement.setState(hotelManagement.getCheckInState());   //状态变成已经入住  
	    }  
	  
	    public void checkOutRoom() {  
	        //不需要做操作  
	    }  
	  
	    public void unsubscribeRoom() {  
	        //不需要做操作  
	    }  
	  
	}