国王和100个犯人-

已经失业半年的

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灯

package justforfun;

public class Light {
    private static Light _light; // 电灯
    private boolean _state; // 电灯的状态

    private Light() {
        _state = false; // 默认是关闭的
    }

    public static Light creatLight() {
        if (_light == null) {
            _light = new Light();
        }
        return _light;
    }

    public void open() {
        _state = true;
    }

    public void close() {
        _state = false;
    }

    public boolean isOpen() {
        return _state;
    }
}

 犯人

package justforfun;

import java.util.Observable;

public class Prisoner extends Observable {
    protected int _no; // 犯人的编号
    private boolean _operationFlag; // 是否进行过操作

    public Prisoner(int no) {
        _no = no;
        _operationFlag = false;
    }

    public void operation(Light light) {
        if (!_operationFlag && !light.isOpen()) {
            light.open();
            _operationFlag = true;
        }
    }

    public static Counter upgradeToCounter(Prisoner prisoner, int size) {
        return new Counter(prisoner._no, size);
    }
}

 计数者

package justforfun;

public class Counter extends Prisoner {
    private int _count = 0; // 关灯的次数
    private int _maxCount; // 监狱中罪犯的人数

    public Counter(int no, int maxCount) {
        super(no);
        _maxCount = maxCount;
    }

    @Override
    public void operation(Light light) {
        if (light.isOpen()) {
            light.close();
            _count++;
            if (isEnd()) {
                setChanged();
                notifyObservers("所有的犯人都出来放过风了");
            }
        }
    }

    private boolean isEnd() {
        return _count == _maxCount - 1;
    }
}

监狱

package justforfun;

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

public class Prison {
    private List<Prisoner> _prison; // 监狱
    private int _size; // 监狱大小
    private static final int INIT_SIZE = 100; // 监狱初始大小为100

    public Prison() {
        this(INIT_SIZE);
    }

    public Prison(int size) {
        _size = size;
        _prison = new ArrayList<Prisoner>(_size);
    }

    public boolean addPrisoner(Prisoner prisoner) {
        if (_prison.size() >= _size) {
            throw new RuntimeException("监狱已满！请申请扩建。");
        } else {
            _prison.add(prisoner);
            return true;
        }
    }

    public void replacePrisoner(Prisoner prisoner) {
        _prison.set(prisoner._no, prisoner);
    }

    public Prisoner getPrisoner(int no) {
        if (no > _prison.size()) {
            throw new RuntimeException("对不起！没有你要找的人。");
        } else {
            return _prison.get(no);
        }
    }

    public int getPrisonSize() {
        return _prison.size();
    }
}

国王

package justforfun;

import java.util.Observable;
import java.util.Observer;
import java.util.Random;

public class King implements Observer {
    boolean isEnd = false; // 是否结束
    public static final int PRISON_SIZE = 100;

    public static void main(String[] args) {
        King king = new King();
        Prison prison = initPrison(king);
        meeting(king, prison); // 犯人们在开会
        int day = start(king, prison);
        System.out.println("过去了" + day / 365 + "年" + day % 365 + "天， 犯人们都解放了");
    }

    private static int start(King king, Prison prison) {
        Light light = Light.creatLight();
        // 无尽的日子开始了...
        int day = 0;
        while (!king.isEnd) {
            // 煎熬中...
            prison.getPrisoner(new Random().nextInt(PRISON_SIZE)).operation(
                    light);
            day++;
        }
        return day;
    }

    // 先抓点犯人扔进监狱
    private static Prison initPrison(King king) {
        Prison prison = new Prison(PRISON_SIZE);
        for (int i = 0; i < PRISON_SIZE; i++) {
            Prisoner prisoner = new Prisoner(i);
            prisoner.addObserver(king);
            prison.addPrisoner(prisoner);
        }
        return prison;
    }

    private static void meeting(King king, Prison prison) {
        Prisoner specialPrisoner = prison.getPrisoner(new Random()
                .nextInt(PRISON_SIZE)); // 选出一个犯人
        specialPrisoner = Prisoner.upgradeToCounter(specialPrisoner, prison
                .getPrisonSize()); // 犯人升级为计数者
        specialPrisoner.addObserver(king);
        prison.replacePrisoner(specialPrisoner);
    }

    // 接收来自犯人的通知
    @Override
    public void update(Observable prisoner, Object content) {
        System.out.println(content);
        isEnd = true;
    }
}