有些太简单了，没有感觉，虽然是保存状态恢复状态，但是主要应该说明类之间的交互关系，这样才是行为型设计模式应该说明和引导理解的关键点。
Topic source简单示例，描述 Originator 和 Memento 和Caretaker 的交互。
snapshot（Memento ）
package demo.designpattern.act.memento.editor;
public final class Snapshot {
private Editor editor;
private String text, curX, curY, selectionWidth;
public Snapshot(Editor editor, String text, String curX, String curY, String selectionWidth) {
this.editor = editor;
this.text = text;
this.curX = curX;
this.curY = curY;
this.selectionWidth = selectionWidth;
}
public void restore() {
editor.setText(text);
editor.setPosition(curX, curY);
editor.setSelectionWidth(selectionWidth);
}
}
Originator
package demo.designpattern.act.memento.editor;
public class Editor {
private String text, curX, curY, selectionWidth;
public void setText(String text) {
this.text = text;
}
public void setPosition(String x, String y) {
this.curX = x;
this.curY = y;
}
public void setSelectionWidth(String selectionWidth) {
this.selectionWidth = selectionWidth;
}
public void createSnapshot() {
Snapshot snapshot = new Snapshot(this, text, curX, curY, selectionWidth);
History.push(snapshot);
}
public void restore() {
Snapshot pop = History.pop();
if (pop != null) {
pop.restore();
}
}
@Override
public String toString() {
return "Editor{" +
"text='" + text + '\'' +
", curX='" + curX + '\'' +
", curY='" + curY + '\'' +
", selectionWidth='" + selectionWidth + '\'' +
'}';
}
}
Caretaker
package demo.designpattern.act.memento.editor;
import java.util.LinkedList;
public final class History {
private final static LinkedList<Snapshot> snapshots = new LinkedList<>();
public static boolean push(Snapshot snapshot) {
return snapshots.offer(snapshot);
}
public static Snapshot pop() {
return snapshots.poll();
}
}
测试demo
package demo.designpattern.act.memento.editor;
public class demo {
public static void main(String[] args) {
Editor editor = new Editor();
editor.setText("修改前");
editor.setPosition("1","2");
editor.setSelectionWidth("12");
editor.createSnapshot();
System.out.println(editor.toString());
System.out.println("---------------------");
editor.setText("修改后");
editor.setPosition("2","1");
editor.setSelectionWidth("34");
System.out.println(editor.toString());
System.out.println("---------------------");
editor.restore();
System.out.println(editor.toString());
}
}
测试输出
Editor{text='修改前', curX='1', curY='2', selectionWidth='12'}
---------------------
Editor{text='修改后', curX='2', curY='1', selectionWidth='34'}
---------------------
Editor{text='修改前', curX='1', curY='2', selectionWidth='12'}
- 1
两把刷子闯江湖
有些太简单了，没有感觉，虽然是保存状态恢复状态，但是主要应该说明类之间的交互关系，这样才是行为型设计模式应该说明和引导理解的关键点。