JAVA编程思想第四版-多线程的练习答案之练习19

最新推荐文章于 2020-05-16 00:33:41 发布

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最新推荐文章于 2020-05-16 00:33:41 发布

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分类专栏： JAVA编程思想 21多线程文章标签： JAVA编程思想多线程练习

本文链接：https://blog.youkuaiyun.com/ltp2010/article/details/15750907

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本文通过一个具体的Java并发示例，展示了如何使用synchronized关键字来保护共享资源，并利用多线程进行计数器的增量操作。同时介绍了如何利用ExecutorService管理线程池，并通过sleep和yield方法控制线程的执行节奏。

package exercise.exercise19;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static net.mindview.util.Print.*;

class Count {

	private int count = 0;
	private Random rand = new Random(47);

	public synchronized int increment() {
		int temp = count;
		if (rand.nextBoolean()) {
			Thread.yield();
		}
		return (count = ++temp);
	}

	public synchronized int value() {
		return count;
	}

}

class Entrance implements Runnable {

	private static Count count = new Count();
	private static List<Entrance> entrances = new ArrayList<Entrance>();
	private int number = 0;

	private final int id;

	// private static volatile boolean canceled = false;

	// public static void canceld(){
	// canceled =true;
	// }

	public Entrance(int id) {
		this.id = id;
		entrances.add(this);
	}

	@Override
	public void run() {
		// while (!canceled) {
		try {
			while (true) {
				synchronized (this) {
					++number;
				}
				print(this + " Total:" + count.increment());
				TimeUnit.MILLISECONDS.sleep(100);
			}
		} catch (InterruptedException e) {
			print("sleep interrupted");
		}
		print("stop " + this);

	}

	public synchronized int getValue() {
		return number++;
	}

	@Override
	public String toString() {
		return "Entrance " + id + ": " + getValue();
	}

	public static int getTotalCount() {
		return count.value();
	}

	public static int sumEntrances() {
		int sum = 0;
		for (Entrance entrance : entrances) {
			sum += entrance.getValue();
		}
		return sum;
	}

}

public class OrnamentalGarden {
	public static void main(String[] args) {
		ExecutorService exec = Executors.newCachedThreadPool();

		for (int i = 0; i < 5; i++) {
			exec.execute(new Entrance(i));
		}
		try {
			TimeUnit.SECONDS.sleep(3);
		} catch (InterruptedException e) {

		}
		// Entrance.canceld();
		// exec.shutdown();
		exec.shutdownNow();
		try {
			if (!exec.awaitTermination(250, TimeUnit.MILLISECONDS)) {
				print("Some tasks were not terminated!");
			}
		} catch (InterruptedException e) {
			e.printStackTrace();
		}

		print("Total: " + Entrance.getTotalCount());
		print("Sum of Entrances:" + Entrance.sumEntrances());

	}
}

注释掉之前的cancel标记即可。把关闭的ExecutorService的方法改为shutdownNow即可。