java 多线程小练

在网上看到这样一道试题,关于多线程的,拿来小练一下
题目:有一个南北向的桥，只能容纳一个人，现桥的两边分别有10人和12人，编制一个多线程序让这些人到达对岸，每个人用一个线程表示，桥为共享资源。在过桥的过程中显示谁在过桥及其走向。

以下是我的代码

package test;

public class MyThread3 extends Thread {

	private String name;
	private String direction;

	public MyThread3(String name, String direction) {
		this.direction = direction;
		this.name = name;
		System.out.println(direction + "方的" + name + "开始过桥...");
	}

	public synchronized void run() {
		try {
			Thread.currentThread().sleep(100);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println(this.direction + "方的" + this.name + "过桥完成!"+"---"+Thread.currentThread().getName());
	}

	public static void main(String[] args) throws InterruptedException {
		MyThread3[] ths = new MyThread3[12];
		int i = 0;
		boolean flag = true;
		while (i <ths.length) {
			if (i < 10)
				ths[i] = new MyThread3("第" + (i+1) + "个人",flag == false ? "北" : "南");
			else
				ths[i] = new MyThread3("第" + (i+1) + "个人", "南");
			ths[i].start();
			ths[i].join();
			ths[i].sleep(1000);
			flag = !flag;
			if (flag == true||i>=10)
				i++;
		}
	}
}

对于synchronized 关键字用法还没完全搞懂,在run中可有可无的

评论

2 楼 java_user 2011-05-12  

写了一个，你可以参考一下

package test;

public class TheBridge {

	public static void main(String[] args) {
		Bridge bridge = new Bridge();
		for (int i = 0; i < 22; i++) {
			if (i < 10) {
				new PersonCrossBridge("人" + i, bridge, 1).start();
			} else {
				new PersonCrossBridge("人" + i, bridge, -1).start();
			}
		}
	}

}

class PersonCrossBridge extends Thread {
	private String personName;
	private Bridge bridge;
	private int direction;

	public PersonCrossBridge(String personName, Bridge bridge, int direction) {
		this.personName = personName;
		this.bridge = bridge;
		this.direction = direction;
	}

	public void run() {
		if (direction > 0) {
			bridge.crossFromS2N(personName);
		} else {
			bridge.crossFromN2S(personName);
		}
	}
}

class Bridge {
	public synchronized void crossFromS2N(String person) {
		System.out.print(person + "从南面开始");
		try {
			//模拟过桥
			Thread.sleep(500);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("---到达北面");
	}

	public synchronized void crossFromN2S(String person) {
		System.out.print(person + "从北面开始");
		try {
			//模拟过桥
			Thread.sleep(500);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		System.out.println("---到达南面");
	}
}

1 楼 java_user 2011-05-12  

说通俗点，synchronized 是用来让线程在访问同一资源时排队，防止造成冲突