多线程的问题

[太上-道]

求大神给个代码，有100，每次让子线程执行20,执行完后再次分配给子线程20，直到没有！

[zs808]

你说的是令牌桶(Token Bucket)的实现吧。 下面是一个最简单的示例实现：

package org.imzhs.learn.test;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

public class App {
	static AtomicInteger tokens = new AtomicInteger(100); //初始100个令牌
	static Random rnd = new Random();
	static CountDownLatch latch; //用来监视线程执行完毕的latch
	
	static class Consumer implements Runnable{
		int requireToken(){
			while(true){
				int currentToken = tokens.get();
				if(currentToken >= 20){
					int newToken = currentToken - 20;
					//CAS更新令牌桶，如果更新失败，证明有其它线程消费Token了，需要重新进行获取尝试
					if(tokens.compareAndSet(currentToken, newToken)){
						return newToken;
					}
				}
				Thread.yield(); //给予其它线程执行的机会
			}
		}
		
		int releaseToken(){
			return tokens.addAndGet(20);
		}
		
		@Override
		public void run() {
			//获取令牌
			int currentTokens = requireToken();
			System.out.println("线程 " + Thread.currentThread().getId() + " 获取Token，剩余" + currentTokens);
			//随机休眠1-2秒，模拟线程执行情况
			int sleepSecs = 1 + rnd.nextInt(2);
			System.out.println("线程 " + Thread.currentThread().getId() + " 休眠 " + sleepSecs + "秒");
			try {
				Thread.sleep(sleepSecs * 1000);
			} catch (InterruptedException e) {
			} finally {
				//销毁令牌
				currentTokens = releaseToken();
				System.out.println("线程 " + Thread.currentThread().getId() + " 释放Token，剩余" + currentTokens);
				latch.countDown();
			}
		}
		
	}
	
	public static void main(String[] args) {
		//开始模拟
		latch = new CountDownLatch(100);
		for (int i = 0; i < 100; i++) {
			Thread th = new Thread(new Consumer());
			th.start();
		}
		
		try {
			latch.await();//阻塞主线程，直到所有线程执行完毕
		} catch (InterruptedException e) {
		} finally {
			System.out.println("所有线程执行完毕，剩余Token：" + tokens.get()); //此时token数应该为初始容量（100）
		}
	}
}

[zs808]

为了更直观点，在线程开始执行的时候加了一个print，代码如下：

package org.imzhs.learn.test;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

public class App {
	static AtomicInteger tokens = new AtomicInteger(100); //初始100个令牌
	static Random rnd = new Random();
	static CountDownLatch latch; //用来监视线程执行完毕的latch
	
	static class Consumer implements Runnable{
		int requireToken(){
			while(true){
				int currentToken = tokens.get();
				if(currentToken >= 20){
					int newToken = currentToken - 20;
					//CAS更新令牌桶，如果更新失败，证明有其它线程消费Token了，需要重新进行获取尝试
					if(tokens.compareAndSet(currentToken, newToken)){
						return newToken;
					}
				}
				Thread.yield(); //给予其它线程执行的机会
			}
		}
		
		int releaseToken(){
			return tokens.addAndGet(20);
		}
		
		@Override
		public void run() {
			System.out.println("线程 " + Thread.currentThread().getId() + " 开始执行");
			//获取令牌
			int currentTokens = requireToken();
			System.out.println("线程 " + Thread.currentThread().getId() + " 获取Token，剩余" + currentTokens);
			//随机休眠1-2秒，模拟线程执行情况
			int sleepSecs = 1 + rnd.nextInt(2);
			System.out.println("线程 " + Thread.currentThread().getId() + " 休眠 " + sleepSecs + "秒");
			try {
				Thread.sleep(sleepSecs * 1000);
			} catch (InterruptedException e) {
			} finally {
				//销毁令牌
				currentTokens = releaseToken();
				System.out.println("线程 " + Thread.currentThread().getId() + " 释放Token，剩余" + currentTokens);
				latch.countDown();
			}
		}
		
	}
	
	public static void main(String[] args) {
		//开始模拟
		latch = new CountDownLatch(100);
		for (int i = 0; i < 100; i++) {
			Thread th = new Thread(new Consumer());
			th.start();
		}
		
		try {
			latch.await();//阻塞主线程，直到所有线程执行完毕
		} catch (InterruptedException e) {
		} finally {
			System.out.println("所有线程执行完毕，剩余Token：" + tokens.get()); //此时token数应该为初始容量（100）
		}
	}
}