[Java知识库]Java Future多线程

Future的get()方法是阻塞的, 需要优化才可以实现异步多线程, 示例如下所示.

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class TestFuture {
	private static final int THREAD_SIZE = 10;
	private static final int USER_NUM = 55;

	public static void main(String[] args) {
		ExecutorService executor = Executors.newFixedThreadPool(THREAD_SIZE);	//线程池
		List<Future<Boolean>> futureList = new ArrayList<>(THREAD_SIZE);	//future缓存队列
		int count = (int)Math.ceil((USER_NUM*1.0f)/THREAD_SIZE);
		System.out.println("count="+count);
		for (int i = 0; i < count; i++) {
			for (int j = 0; j < THREAD_SIZE; j++) {
				CountNum countNum = new CountNum();
				Future<Boolean> future = executor.submit(countNum);
				futureList.add(future);
			}
			for(Future<Boolean> f: futureList){
				try {
					Boolean ret = f.get();	//会阻塞
				} catch (InterruptedException | ExecutionException e) {
					e.printStackTrace();
				}
			}
		}
		executor.shutdown();	//关闭线程池
		System.out.println("================");
	}
}

//具体线程任务
class CountNum implements Callable<Boolean>{
	@Override
	public Boolean call() throws Exception {
		System.out.println(Thread.currentThread().getId()+" start");
		Thread.sleep(50);
		System.out.println(Thread.currentThread().getId()+" end");
		return true;
	}
}