Future实例

package concurrent.Future;

import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
/**
 * Future会等待提交的线程执行之后获取到返回数据
 *
 */
public class FutureTest {
	public static void main(String[] args) throws Exception{
//		method1();
//		method2();
		method3();
	}
	
	public static void method1() throws Exception{
		ExecutorService pool=Executors.newFixedThreadPool(3);
		
		//使用completion提交callable时,一次提交一组callable,使用take方法来取,只要有一个任务运行完了就可以获取
		CompletionService<String> completion=new ExecutorCompletionService<String>(pool);
		
		Future<String> future=completion.submit(new Callable<String>() {
			@Override
			public String call() throws Exception {
				Thread.sleep(2000);
				return "hello";
			}
		});
		System.out.println("等待结果");
		System.out.println(future.get());
		System.out.println(completion.take().get());
	}
	
	public static void method2() throws Exception{
		ExecutorService pool=Executors.newSingleThreadExecutor();
		Future<String> future=pool.submit(new Callable<String>() {
			@Override
			public String call() throws Exception {
				Thread.sleep(2000);
				return "abcdefg";
			}
		});
		System.out.println("等待结果");
		//System.out.println(future.get());
		
		//如果1秒之内还拿不到结果，就会抛异常java.util.concurrent.TimeoutException
		System.out.println(future.get(1, TimeUnit.SECONDS));
	}
	
	/**
	 * 提交多个任务 
	 * 这里是一次提交10个任务
	 */
	public static void method3() throws Exception{
		ExecutorService pool=Executors.newFixedThreadPool(10);
		CompletionService<String> completion=new ExecutorCompletionService<String>(pool);
		for(int i=1;i<=10;i++){
			final int task=i;
			completion.submit(new Callable<String>() {
				
				@Override
				public String call() throws Exception {
					Thread.sleep(1000);
					return "我是任务："+task;
				}
			});
		}
		for(int i=0;i<10;i++){
			System.out.println(completion.take().get());
		}
	}
}