Java设计模式：备忘录模式，历史记录状态回滚回退

冷不防 2023-11-23 06:23 211阅读 0赞

以棋类游戏中的“悔棋”为例。

public class Chessman {
    	private String tag;
    	private int point;
    
    	public void set(String tag, int point) {
    		this.tag = tag;
    		this.point = point;
    	}
    
    	// 保存状态。
    	public ChessmanMemory save() {
    		return new ChessmanMemory(this.tag, this.point);
    	}
    
    	// 恢复状态。
    	public void restore(ChessmanMemory memory) {
    		this.tag = memory.getTag();
    		this.point = memory.getPoint();
    	}
    
    	// 输出结果。
    	public void display() {
    		System.out.println(tag + "-" + point);
    	}
    }

public class ChessmanMemory {
    	private String tag;
    	private int point;
    
    	public ChessmanMemory(String tag, int point) {
    		this.tag = tag;
    		this.point = point;
    	}
    
    	public int getPoint() {
    		return point;
    	}
    
    	public String getTag() {
    		return tag;
    	}
    }

import java.util.Stack;
    
    public class MemoryManager {
    	// 保存的状态Java栈。
    	private Stack<ChessmanMemory> memoryStack = new Stack<>();
    
    	public ChessmanMemory getMemory() {
    		return memoryStack.pop();
    	}
    
    	public void addMemory(ChessmanMemory memory) {
    		memoryStack.push(memory);
    	}
    }

public class Test {
    	public Test() {
    		MemoryManager manager = new MemoryManager();
    
    		// A
    		Chessman chessman = new Chessman();
    		chessman.set("A", 1);
    		chessman.display();
    		manager.addMemory(chessman.save());
    
    		// A-B
    		chessman.set("B", 2);
    		chessman.display();
    		manager.addMemory(chessman.save());
    
    		// A-B-C
    		chessman.set("C", 3);
    		chessman.display();
    		manager.addMemory(chessman.save());
    
    		System.out.println("状态回退");
    		// C
    		chessman.restore(manager.getMemory());
    		chessman.display();
    
    		// C-B
    		System.out.println("状态回退");
    		chessman.restore(manager.getMemory());
    		chessman.display();
    
    		// C-B-A
    		System.out.println("状态回退");
    		chessman.restore(manager.getMemory());
    		chessman.display();
    	}
    
    	public static void main(String[] args) {
    		new Test();
    	}
    }

输出：

A-1
    B-2
    C-3
    状态回退
    C-3
    状态回退
    B-2
    状态回退
    A-1