java设计模式——备忘录模式

《大话设计模式》第十八章

package ch18;

public class Memento {
	private String state;

	public Memento(String state) {
		this.state = state;
	}

	public String getState() {
		return state;
	}
}

 

package ch18;

public class Originator {
	private String state;

	public String getState() {
		return state;
	}

	public void setState(String state) {
		this.state = state;
	}
	
	public Memento createMemento() {
		return new Memento(state);
	}
	
	public void setMemento(Memento memento) {
		state = memento.getState();
	}
	
	public void show() {
		System.out.println("State = " + state);
	}
}

 

package ch18;

public class Caretaker {
	private Memento memento;

	public Memento getMemento() {
		return memento;
	}

	public void setMemento(Memento memento) {
		this.memento = memento;
	}
}

 

package ch18;

public class Client {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Originator o = new Originator();
		o.setState("on");
		o.show();
		
		Caretaker c = new Caretaker();
		c.setMemento(o.createMemento());
		o.setState("off");
		o.show();
		
		o.setMemento(c.getMemento());
		o.show();
	}

}

运行：

State = on
State = off
State = on

在JDK中，我们可以通过实现java.io.Serializable接口来保存对象的状态。