介绍
概念:在不破坏封装性的前提下,捕获一个对象的内部状态,并在该对象之外保存这个状态。这样以后就可将该对象恢复到原先保存的状态。
应用场景:需要保存某个对象的某个时间的状态,如游戏的暂停,存档,恢复功能. 如果把数据库与实体关联起来了,也可以说数据库是这个对象的备忘录.
接来下实现一个游戏存档与读档的功能
代码:
//游戏类
package note.com.memento;
import java.math.BigDecimal;
import java.util.ArrayList;
public class DiningRoom {
private Integer waiter = 1;//服务员初始1
private String name = "default";//默认名称
private BigDecimal money = new BigDecimal(500);//初始金钱500
private ArrayList<String> foods = new ArrayList<String>();
public DiningRoom(){
foods.add("小鸡炖蘑菇");
foods.add("剁椒鱼头");
foods.add("狗不理包子");
}
/*
* 读档
*/
public DiningRoom(SaveGame game){
this.waiter = game.getWaiter();
this.name = game.getName();
this.money = game.getMoney();
this.foods = game.getFoods();
System.out.println("读取档案....");
draw();
}
/*
* 开始游戏
*/
public void start(){
System.out.println("游戏开始......");
draw();
}
public void draw(){
System.out.println("绘制显示......");
}
public void openDoor(){
System.out.println("开业");
}
public void closeDoor(){
System.out.println("打烊");
}
/*
* 恢复游戏
*/
public void back(SaveGame game){
this.waiter = game.getWaiter();
this.name = game.getName();
this.money = game.getMoney();
this.foods = game.getFoods();
System.out.println("恢复档案...");
draw();
}
/*
* 存档
*/
public SaveGame save(){
return new SaveGame(this);
}
public void show(){
System.out.println("餐厅名称:"+this.name);
System.out.println("余额:"+this.money.toString());
System.out.println("服务员:"+this.waiter+"人");
}
public Integer getWaiter() {
return waiter;
}
public void setWaiter(Integer waiter) {
this.waiter = waiter;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public BigDecimal getMoney() {
return money;
}
public void setMoney(BigDecimal money) {
this.money = money;
}
public ArrayList<String> getFoods() {
return foods;
}
public void setFoods(ArrayList<String> foods) {
this.foods = foods;
}
}
//存档实体
package note.com.memento;
import java.math.BigDecimal;
import java.util.ArrayList;
/**
* 存档
* @author lxz
*
*/
public class SaveGame {
private Integer waiter = 1;//服务员初始1
private String name = "default";//默认名称
private BigDecimal money = new BigDecimal(500);//初始金钱500
private ArrayList<String> foods = new ArrayList<String>();
public SaveGame(DiningRoom room){
this.waiter = room.getWaiter();
this.name = room.getName();
this.money = room.getMoney();
this.foods = room.getFoods();
}
public Integer getWaiter() {
return waiter;
}
public void setWaiter(Integer waiter) {
this.waiter = waiter;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public BigDecimal getMoney() {
return money;
}
public void setMoney(BigDecimal money) {
this.money = money;
}
public ArrayList<String> getFoods() {
return foods;
}
public void setFoods(ArrayList<String> foods) {
this.foods = foods;
}
}
//测试类
package note.com.memento;
import java.math.BigDecimal;
public class MementoTest {
public static void main(String[] args) {
DiningRoom game = new DiningRoom();
game.show();
game.start();
game.setMoney(new BigDecimal(2000));
game.setName("小洋人");
game.show();//显示当前状态
SaveGame save1 = game.save();
game.setName("大洋人");
game.show();//显示当前状态
game.back(save1);//恢复到修改名称之前
game.show();//恢复后状态
//===================重新打开游戏
System.out.println("=====重新开始=======");
DiningRoom game2 = new DiningRoom(save1);//重新打开游戏读取存档
game2.show();//存档状态
}
}
//结果
餐厅名称:default
余额:500
服务员:1人
游戏开始......
绘制显示......
餐厅名称:小洋人
余额:2000
服务员:1人
餐厅名称:大洋人
余额:2000
服务员:1人
恢复档案...
绘制显示......
餐厅名称:小洋人
余额:2000
服务员:1人
=====重新开始=======
读取档案....
绘制显示......
餐厅名称:小洋人
余额:2000
服务员:1人
备忘录模式是比较容易理解的了.