【筆記】使用Java練習觀察者模式(Observer pattern)

Subject.java

package idv.jk.study.designpattern.observer;

import java.util.ArrayList;
import java.util.List;

public abstract class Subject
{
    private String mMessage;
    List mObserverList = new ArrayList();

    public void add(Observer observer)
    {
        mObserverList.add(observer);
    }

    public void remove(Observer observer)
    {
        mObserverList.remove(observer);
    }

    public void broadcast()
    {
        for(Observer o : mObserverList)
        {
            o.update();
        }
    }

    public String getMessage()
    {
        return mMessage;
    }

    public void setMessage(String message)
    {
        this.mMessage = message;
    }
}

Observer.java

package idv.jk.study.designpattern.observer;

public abstract class Observer
{
    protected String mName;
    protected Subject mSubject;

    public abstract void update();
}

Sheep.java

package idv.jk.study.designpattern.observer;

public class Sheep extends Observer
{
    public Sheep(String name, Subject subject)
    {
        this.mName = name;
        this.mSubject = subject;
        subject.add(this);
    }

    @Override
    public void update()
    {
        System.out.printf("通知 %s：%s%n", mName, mSubject.getMessage());
    }
}

SheepDog.java

package idv.jk.study.designpattern.observer;

public class SheepDog extends Subject
{
}

Main.java

package idv.jk.study.designpattern.observer;

public class Main
{
    public static void main(String[] args)
    {
        //Shaun the sheep中的那隻牧羊犬
        SheepDog bitzer = new SheepDog();

        //chief actor
        Sheep shaun = new Sheep("Shaun", bitzer);

        //Shaun's cousin, is the flock's only lamb,
        Sheep timmy = new Sheep("Timmy", bitzer);

        //Shirley is the largest member of the flock
        Sheep shirley = new Sheep("Shirley", bitzer);

        //Nuts, is quite an eccentric, but useful sheep and usually like the rest of the flock, accompanies and helps Shaun.
        Sheep nuts = new Sheep("Nuts", bitzer);

        bitzer.setMessage("主人回來了，快點恢復正常羊的樣子");
        bitzer.broadcast();

        System.out.println("晚上了...");
        //晚上了，Timmy比較早睡，Bitzer就不通知他
        bitzer.remove(timmy);
        bitzer.setMessage("星星出來了，大家快來看啊");
        bitzer.broadcast();
    }
}

【筆記】用Java實作備忘錄(memoto)模式的簡單範例

嘗試用說故事的方弍來寫看看，XD Main.java

package idv.jk.study.designpattern.memoto;

/**
 * Created by bioyang on 2015/10/12.
 */
public class Main
{
    public static void main(String[] args)
    {
        //有一個叫小明的工程師
        Programmer smallMing = Programmer.beforeWork();
        //他在上班前的身心狀態
        System.out.printf("開始工作前的HP為 %d, 憤怒條為 %d\r\n", 
                            smallMing.getHitPoint(), smallMing.getAngryPoint());

        //為了確認明天是全新的一天，他的大腦要把上班前的狀態給記下來
        ProgrammerBrain brainOfSmallMing = new ProgrammerBrain();
        brainOfSmallMing.setBodyStateMemoto(smallMing.getBodyStateMemoto());

        //小明修了一個Bug
        smallMing.fixBug();
        //這對他的身心狀態沒有太大的影響
        System.out.printf("修了一個Bug的HP為 %d, 憤怒條為 %d\r\n", 
                            smallMing.getHitPoint(), smallMing.getAngryPoint());

        //客戶改了需求
        smallMing.requirementChanged();
        //要殺死一個工程師，只要改一個需求
        System.out.printf("知道客戶改了需求後的HP為 %d, 憤怒條為 %d\r\n", 
                            smallMing.getHitPoint(), smallMing.getAngryPoint());

        //但一天過去了，又是美好、新的一天
        smallMing.recoverBodyStateMemoto(brainOfSmallMing.getBodyStateMemoto());
        System.out.printf("隔天起床工作前的HP為 %d, 憤怒條為 %d\r\n", 
                            smallMing.getHitPoint(), smallMing.getAngryPoint());
    }
}

Programmer.java

package idv.jk.study.designpattern.memoto;

/**
 * Created by bioyang on 2015/10/12.
 */
public class Programmer
{
    /**
     * 生命值
     */
    private int hitPoint;
    /**
     * 憤怒條
     */
    private int angryPoint;

    private BodyStateMemoto mBodyStateMemoto;

    public BodyStateMemoto saveState()
    {
        return new BodyStateMemoto(this.hitPoint, this.angryPoint);
    }

    public static Programmer beforeWork()
    {
        Programmer programmer = new Programmer();
        programmer.setHitPoint(100);
        programmer.setAngryPoint(0);
        return programmer;
    }

    public void fixBug()
    {
        this.hitPoint -= 5;
        this.angryPoint += 10;
    }

    public void requirementChanged()
    {
        this.hitPoint = 0;
        this.angryPoint = 200;
    }

    public BodyStateMemoto getBodyStateMemoto()
    {
        return new BodyStateMemoto(getHitPoint(), getAngryPoint());
    }

    public void recoverBodyStateMemoto(BodyStateMemoto bodyStateMemoto)
    {
        setHitPoint(bodyStateMemoto.getHitPoint());
        setAngryPoint(bodyStateMemoto.getAngryLevel());
    }

    public int getHitPoint()
    {
        return hitPoint;
    }

    public void setHitPoint(int hitPoint)
    {
        this.hitPoint = hitPoint;
    }

    public int getAngryPoint()
    {
        return angryPoint;
    }

    public void setAngryPoint(int angryPoint)
    {
        this.angryPoint = angryPoint;
    }
}

BodyStateMemoto.java

package idv.jk.study.designpattern.memoto;

/**
 * Created by bioyang on 2015/10/12.
 */
public class BodyStateMemoto
{
    /**
     * 生命力
     */
    private int hitPoint;
    /**
     * 憤怒值
     */
    private int angryLevel;

    public BodyStateMemoto(int hitPoint, int angryLevel)
    {
        this.hitPoint = hitPoint;
        this.angryLevel = angryLevel;
    }

    public int getHitPoint()
    {
        return hitPoint;
    }

    public void setHitPoint(int hitPoint)
    {
        this.hitPoint = hitPoint;
    }

    public int getAngryLevel()
    {
        return angryLevel;
    }

    public void setAngryLevel(int angryLevel)
    {
        this.angryLevel = angryLevel;
    }
}

ProgrammerBrain.java

package idv.jk.study.designpattern.memoto;

/**
 * Created by bioyang on 2015/10/12.
 */
public class ProgrammerBrain
{
    private BodyStateMemoto mBodyStateMemoto;

    public void setBodyStateMemoto(BodyStateMemoto bodyStateMemoto)
    {
        this.mBodyStateMemoto = bodyStateMemoto;
    }

    public BodyStateMemoto getBodyStateMemoto()
    {
        return mBodyStateMemoto;
    }
}