public interface ExecutorService extends Executor {...}
ExecutorService#submit有三个重载方法,之前一直没注意,今天仔细以研究,还是有好些知识点的
1.第一个就不说了
<T> Future<T> submit(Callable<T> task);
2.返回的future#get会阻塞,得到的结果就是result
<T> Future<T> submit(Runnable task, T result);
3.future#get也是会阻塞的,只是返回的结果是null
Future<?> submit(Runnable task);
a.FutureTask是Future的唯一实现
public class FutureTask<V> implements RunnableFuture<V> {...}
public interface RunnableFuture<V> extends Runnable, Future<V> {...}
code demo
ExecutorService executor = Executors.newSingleThreadExecutor(); Future future = executor.submit(new Runnable() { public void run() { System.out.println("run"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } }); System.out.println(future.get()); final List<String> list = Lists.newArrayList("a", "b"); Future future2 = executor.submit(new Runnable() { public void run() { list.add("c"); System.out.println("run with result"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } }, list); System.out.println(future2.get()); executor.shutdown();
执行结果
run null run with result [a, b, c]