Java线程学习笔记（二）

从任务中产生返回值

Runnable是执行工作的独立任务，不返回任何值，如果希望任务结束后能够返回一个值，应该实现Callable接口，并且通过ExecutorService.submit()调用，并返回一个Future<T>对象

 

package com.woxiaoe.study.thread;

import java.util.concurrent.Callable;

/**
 * 计数类2可以返回值
 * @author 小e
 *
 * 2010-4-19 下午09:55:12
 */
public class Counter2 implements Callable<String> {
	private int countNum;
	private static int taskCount = 0;//线程id
	private final int taskId = taskCount++;
	
	public Counter2(int countNum) {
		this.countNum = countNum;
	}
	
	public String show(){
		return "Id[" + taskId + "] countNum:" + countNum + "  ";
	}
	@Override
	public String call() throws Exception {
		String result = null;
		while(countNum-- > 0){
			result = show();
			Thread.yield();
		}
		return result;
	}

}

 测试代码：

public void testCounter2(){
		ExecutorService exec = Executors.newCachedThreadPool();
		List<Future<String>> results = new ArrayList<Future<String>>();
		for(int i = 0; i < 10 ; i++){
			results.add(exec.submit(new Counter2(10)));
		}
		exec.shutdown();
		for (Future<String> future:results) {
			System.out.println(future.isDone());
			try {
				System.out.println(future.get());
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (ExecutionException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				exec.shutdown();
			}
		}
		
	}