设计模式——备忘录模式

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备忘录模式：在不破坏封装的前提下，存储关键对象的重要状态，从而可以在将来把对象还原到存储的那个状态
优点：
状态存储在外面，不和关键对象混在一起，这可以帮助维护内聚
提供了容易实现的恢复能力
保持了关键对象的数据封装
缺点：
资源消耗上面备忘录对象会很昂贵
存储和恢复状态的过程比较耗时

MementoIF .class

public interface public interface MementoIF {}

MementoCaretaker.class

import java.util.HashMap;public class MementoCaretaker {    private HashMap<String, MementoIF> mementomap;    public MementoCaretaker() {        mementomap = new HashMap<String, MementoIF>();    }    public MementoIF retrieveMemento(String name) {        return mementomap.get(name);    }    /**     * 备忘录赋值方法     */    public void saveMemento(String name, MementoIF memento) {        this.mementomap.put(name, memento);    }}

Originator.class

import java.util.HashMap;public class Originator {    private HashMap<String, String> state;    public Originator() {        state = new HashMap();    }    public MementoIF createMemento() {        return new Memento(state);    }    public void restoreMemento(MementoIF memento) {        state = ((Memento) memento).getState();    }    public void showState() {        System.out.println("now state:" + state.toString());    }    public void testState1() {        state.put("blood", "500");        state.put("progress", "gate1 end");        state.put("enemy", "5");    }    public void testState2() {        state.put("blood", "450");        state.put("progress", "gate3 start");        state.put("enemy", "3");    }    private class Memento implements MementoIF {        private HashMap<String, String> state;        private Memento(HashMap state) {            this.state = new HashMap(state);        }        private HashMap getState() {            return state;        }        private void setState(HashMap state) {            this.state = state;        }    }}

Originator2.class

import java.util.ArrayList;public class Originator2 {    private ArrayList<String> state;    public Originator2() {        state = new ArrayList<String>();    }    public MementoIF createMemento() {        return new Memento(state);    }    public void restoreMemento(MementoIF memento) {        state = ((Memento) memento).getState();    }    public void testState1() {        state = new ArrayList<String>();        state.add("blood:320");        state.add("progress:gate2 mid");        state.add("enemy:15");    }    public void testState2() {        state = new ArrayList<String>();        state.add("blood:230");        state.add("progress:gate8 last");        state.add("enemy:12");    }    public void showState() {        System.out.println("now state:" + state.toString());    }    private class Memento implements MementoIF {        private ArrayList<String> state;        private Memento(ArrayList<String> state) {            this.state = new ArrayList(state);        }        private ArrayList<String> getState() {            return state;        }        private void setState(ArrayList<String> state) {            this.state = state;        }    }}

MainTest.class

public class MainTest {    public static void main(String[] args) {        MementoCaretaker mMementoCaretaker = new MementoCaretaker();        Originator mOriginator = new Originator();        Originator2 mOriginator2 = new Originator2();        System.out.println("*****Originator*****");        mOriginator.testState1();        mMementoCaretaker                .saveMemento("Originator", mOriginator.createMemento());        mOriginator.showState();        mOriginator.testState2();        mOriginator.showState();        mOriginator.restoreMemento(mMementoCaretaker                .retrieveMemento("Originator"));        mOriginator.showState();        System.out.println("*****Originator 2*****");        mOriginator2.testState1();        mOriginator2.showState();        mMementoCaretaker.saveMemento("Originator2",                mOriginator2.createMemento());        mOriginator2.testState2();        mOriginator2.showState();        mOriginator2.restoreMemento(mMementoCaretaker                .retrieveMemento("Originator2"));        mOriginator2.showState();        //System.out.println("*****Originator&&Originator 2*****");    //   mOriginator.restoreMemento(mMementoCaretaker    //   .retrieveMemento("Originator2"));    //   mOriginator.showState();    }}

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