java 线程 死锁（哲学家用餐案例讲解） -------thinking java 4，

java 线程 死锁（哲学家用餐案例讲解） -------thinking java 4，

package org.rui.thread.deadlock;
/**
 * 死鎖
 * 
 * 筷子
 * 
 * @author lenovo
 *
 */
public class Chopstick {
	private boolean taken = false;

	public  synchronized void take() throws InterruptedException {
		while (taken) {
			wait();
		}
		taken = true;
	}

	public synchronized void drop() {
		taken = false;
		notifyAll();
	}

}

package org.rui.thread.deadlock;

import java.util.Random;
import java.util.concurrent.TimeUnit;
/**
 * 哲學家
 * @author lenovo
 *
 */
public class Philosopher implements Runnable {

	private Chopstick left;
	private Chopstick right;
	private final int id;
	private final int ponderFactor;// 思考
	private Random rand = new Random(47);

	private void pause() throws InterruptedException {
		
		if (ponderFactor == 0)
			return;
		{
			TimeUnit.MILLISECONDS.sleep(rand.nextInt(ponderFactor * 250));
		}
		
		
		
	}

	public Philosopher(Chopstick left, Chopstick right, int id, int ponderFactor) {
		this.left = left;
		this.right = right;
		this.id = id;
		this.ponderFactor = ponderFactor;
	}

	@Override
	public void run() {

		try {
			while (!Thread.interrupted()) {
				System.out.println(this + " " + "thinking 思考");
				pause();// 暂停

				// philosopher becomes hungry
				System.out.println(this + " " + "grabbing 抓  right");
				right.take();
				System.out.println(this + " " + "grabbing 抓 left");
				left.take();
				System.out.println(this + "" + "eating 吃饭");
				pause();// 暂停
				right.drop();//终止
				left.drop();
			}

		} catch (InterruptedException e) {
			System.out.println(this+" "+"通过中断退出");
		}

	}

	@Override
	public String toString() {
		return " philosopher " + id;
	}

}

package org.rui.thread.deadlock;

import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
 * 這個程序將產生死鎖
 * @author lenovo
 *
 */
public class DeadlockingDiningPhilosophers {

	public static void main(String[] args) throws InterruptedException, IOException {
		String arg[] = { "0", "5","timeout"};
		int ponder = 5;

		if (arg.length > 0) {
			ponder = Integer.parseInt(arg[0]);
		}
		int size = 5;
		if (arg.length > 1) {
			size = Integer.parseInt(arg[1]);
		}

		ExecutorService exec = Executors.newCachedThreadPool();
		Chopstick[] sticks = new Chopstick[size];
		for (int i = 0; i < size; i++) {
			sticks[i] = new Chopstick();
		}
		for (int i = 0; i < size; i++) {
			exec.execute(new Philosopher(sticks[i], sticks[(i + 1) % size], i,
					ponder));
			if(arg.length==3&&arg[2].equals("timeout")){
				TimeUnit.SECONDS.sleep(5);
			}
			else{
				System.out.println("press enter to quit");
			    System.in.read();
			}
			exec.shutdownNow();
		}
	}

}

package org.rui.thread.deadlock;

import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
 * 破壞第四個條件 防止死鎖
 * @author lenovo
 *
 */
public class FixedDiningPhilosophers {

	public static void main(String[] args) throws InterruptedException,
			IOException {

		String[] arg = { "5", "5", "timeout" };

		int ponder = 5;
		if (arg.length > 0) {
			ponder = Integer.parseInt(arg[0]);
		}
		int size = 5;
		if (arg.length > 1) {
			size = Integer.parseInt(arg[1]);
		}

		ExecutorService exec = Executors.newCachedThreadPool();

		Chopstick[] sticks = new Chopstick[size];

		for (int i = 0; i < size; i++) {
			sticks[i] = new Chopstick();
		}

		for (int i = 0; i < size; i++) {
			// 通过确保最后一个philosopher先拿起和放下左边的Chopstick，
			// 我们可以移除死锁，从而使这个程序平滑的运行。
			if (i < (size - 1)) {
				exec.execute(new Philosopher(sticks[i], sticks[i + 1], i,
						ponder));
			} else {
				exec.execute(new Philosopher(sticks[0], sticks[i], i, ponder));
			}
		}

		if (arg.length == 3 && arg[2].equals("timeout")) {
			TimeUnit.SECONDS.sleep(5);
		} else {
			System.out.println("press enter to quit");
			System.in.read();
		}
		exec.shutdownNow();

	}

}