java同步例子之FutureTask
仅在计算完成时才能获取结果；如果计算尚未完成，则阻塞 get 方法。一旦计算完成，就不能再重新开始或取消计算.
package concurrent;import java.util.concurrent.Callable;import java.util.concurrent.ExecutionException;import java.util.concurrent.FutureTask;import java.util.concurrent.TimeUnit;import java.util.concurrent.TimeoutException;/** * FutureTask * * @author user * */public class FutureTaskTest {private final FutureTask<ProductInfo> future = new FutureTask<ProductInfo>(new Callable<ProductInfo>() {public ProductInfo call() throws InterruptedException {return loadProductInfo();}});public ProductInfo loadProductInfo() throws InterruptedException {System.err.println("=====waiting========");Thread.sleep(5000);return new ProductInfo();}private final Thread thread = new Thread(future);public void start() {thread.start();}public ProductInfo get() throws InterruptedException, ExecutionException,TimeoutException {try{return future.get(1, TimeUnit.SECONDS);} catch(TimeoutException e) { //future.cancel(true); //取消任务System.err.println("火速返回，失败！");return future.get(10, TimeUnit.SECONDS);}}/** * @param args * @throws ExecutionException * @throws InterruptedException * @throws TimeoutException */public static void main(String[] args) throws InterruptedException,ExecutionException, TimeoutException {FutureTaskTest test = new FutureTaskTest();test.start();System.err.println("=======begin========");System.err.println(test.get());System.err.println("=======end========");}}class ProductInfo {public String toString() {return "**ProductInfo**";}}