哲学家就餐问题实现

1. 直接对筷子资源进行加锁，只允许一个人同时吃，这种情况只能同时一个人吃

public class PerThread extends Thread {      private static int[] chopstick = { 1, 1, 1, 1, 1 };      private int i;      public PerThread(int i) {          this.i = i;      }      @Override      public void run() {          synchronized (chopstick) {        eat(this.getName());          think(this.getName());          }      }      private void think(String name) {          chopstick[i] = 1;          chopstick[(i + 1) % 5] = 1;          System.out.println("per"+name+" is thinking...");      }      private void eat(String string) {              while (true) {                  if (chopstick[i] != 0) {                      chopstick[i]--;                      System.out.println("per" + this.getName()                              + " got left chopstick.");                      break;                  }              }              try {                  Thread.sleep(1000);              } catch (InterruptedException e) {                  e.printStackTrace();              }              while (true) {                  if (chopstick[(i + 1) % 5] != 0) {                      chopstick[(i + 1) % 5]--;                      System.out.println("per" + this.getName()                              + " got right chopstick.");                      break;                  }              }          System.out.println("per" + string + " is eating...");      }  } 

测试程序

public class Test {    public static void main(String[] args) {        // TODO Auto-generated method stub        for (int i = 0; i < 5; i++) {              Thread t = new PerThread(i);              t.start();          }            }}

2.每个哲学家必须确定自己左右手的筷子都可用的时候，才能同时拿起两只筷子进餐，吃完之后同时放下两只筷子。可以看到最多只能有两条相邻的eating结果，因为每个时刻最多能够满足两个人同时进餐，且两人座位不相邻

class Fork{    /*5只筷子，初始为都未被用*/    private boolean[] used={false,false,false,false,false};    /*只有当左右手的筷子都未被使用时，才允许获取筷子，且必须同时获取左右手筷子*/    public synchronized void takeFork(){        String name = Thread.currentThread().getName();        int i = Integer.parseInt(name);        while(used[i]||used[(i+1)%5]){            try {                wait();//如果左右手有一只正被使用，等待            } catch (InterruptedException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }        used[i ]= true;        used[(i+1)%5]=true;    }    /*必须同时释放左右手的筷子*/    public synchronized void putFork(){        String name = Thread.currentThread().getName();        int i = Integer.parseInt(name);        used[i ]= false;        used[(i+1)%5]=false;        notifyAll();//唤醒其他线程    }}

class Philosopher extends Thread{    private String name;    private Fork fork;    public Philosopher(String name,Fork fork){        super(name);        this.name=name;        this.fork=fork;    }    public void run(){        while(true){            thinking();            fork.takeFork();            eating();            fork.putFork();        }    }    public void eating(){        System.out.println("I am Eating:"+name);        try {            sleep(1000);//模拟吃饭，占用一段时间资源        } catch (InterruptedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    public void thinking(){        System.out.println("I am Thinking:"+name);        try {            sleep(1000);//模拟思考        } catch (InterruptedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

测试程序

public class Test1 {    public static void main(String[] args) {        // TODO Auto-generated method stub          Fork fork = new Fork();            new Philosopher("0",fork).start();            new Philosopher("1",fork).start();            new Philosopher("2",fork).start();            new Philosopher("3",fork).start();            new Philosopher("4",fork).start();    }}

转载自http://www.cnblogs.com/vettel/p/3438257.html