状态模式在软件设计中的应用与实现

2019独角兽企业重金招聘Python工程师标准>>>

以某个酒店系统为例&＃xff0c;酒店的房间有三个状态&＃xff1a;空闲、已预订、已入住&＃xff0c;状态与状态之间可以根据客户的动作来进行转换。

模式定义

在很多情况下&＃xff0c;一个对象的行为取决于它的一个或多个变化的属性&＃xff0c;这些属性我们称之为状态&＃xff0c;这个对象称之为状态对象。对于状态对象而已&＃xff0c;它的行为依赖于它的状态&＃xff0c;比如你要预订房间&＃xff0c;那么只有当该房间为空闲时你才能预订&＃xff0c;你想入住该房间也只有当你预订了该房间或者该房间为空闲时。对于这样的一个对象&＃xff0c;当它在于外部事件产生互动的时候&＃xff0c;其内部状态就会发生改变&＃xff0c;从而使得他的行为也随之发生改变。

那么何为状态模式呢&＃xff1f;所谓状态模式就是允许对象在内部状态发生改变时改变它的行为&＃xff0c;对象看起来好像修改了它的类。

模式结构

模式实现

首先是状态接口&＃xff1a;State

public interface State {/*** &＃64;desc 预订房间* &＃64;return void*/public void bookRoom();/*** &＃64;desc 退订房间* &＃64;return void*/public void unsubscribeRoom();/*** &＃64;desc 入住* &＃64;return void*/public void checkInRoom();/*** &＃64;desc 退房* &＃64;return void*/public void checkOutRoom();}

然后是房间类

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 &＃61; new FreeTimeState(this);checkInState &＃61; new CheckInState(this);bookedState &＃61; new BookedState(this);state &＃61; freeTimeState ; //初始状态为空闲}/*** &＃64;desc 预订房间* &＃64;return void*/public void bookRoom(){state.bookRoom();}/*** &＃64;desc 退订房间* &＃64;return void*/public void unsubscribeRoom(){state.unsubscribeRoom();}/*** &＃64;desc 入住* &＃64;return void*/public void checkInRoom(){state.checkInRoom();}/*** &＃64;desc 退房* &＃64;return void*/public void checkOutRoom(){state.checkOutRoom();}public String toString(){return "该房间的状态是:"&＃43;getState().getClass().getName();}/** getter和setter方法*/public State getFreeTimeState() {return freeTimeState;}public void setFreeTimeState(State freeTimeState) {this.freeTimeState &＃61; freeTimeState;}public State getCheckInState() {return checkInState;}public void setCheckInState(State checkInState) {this.checkInState &＃61; checkInState;}public State getBookedState() {return bookedState;}public void setBookedState(State bookedState) {this.bookedState &＃61; bookedState;}public State getState() {return state;}public void setState(State state) {this.state &＃61; state;}}

然后是3个状态类,这个三个状态分别对于这:空闲、预订、入住。其中空闲可以完成预订和入住两个动作&＃xff0c;预订可以完成入住和退订两个动作&＃xff0c;入住可以退房。

/*** &＃64;project: design_state* &＃64;author chenssy* &＃64;date 2013-8-24* &＃64;Description: 空闲状态只能预订和入住*/
public class FreeTimeState implements State {Room hotelManagement;public FreeTimeState(Room hotelManagement){this.hotelManagement &＃61; hotelManagement;}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}}

/*** &＃64;project: design_state* &＃64;author chenssy* &＃64;date 2013-8-24* &＃64;Description: 入住状态房间只能退房*/
public class BookedState implements State {Room hotelManagement;public BookedState(Room hotelManagement) {this.hotelManagement &＃61; 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}}

/*** &＃64;project: design_state* &＃64;author chenssy* &＃64;date 2013-8-24* &＃64;Description: 入住可以退房*/
public class CheckInState implements State {Room hotelManagement;public CheckInState(Room hotelManagement) {this.hotelManagement &＃61; 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}}

最后是测试类

public class Test {public static void main(String[] args) {//有3间房Room[] rooms &＃61; new Room[2];//初始化for(int i &＃61; 0 ; i

运行结果