前言
Future是一个接口类，定义了5个方法：
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boolean cancel(boolean mayInterruptIfRunning);boolean isCancelled();boolean isDone();V get() throws InterruptedException, ExecutionException;V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException; |
通过这5个方法可以看出，Future不但可以获取提交任务的执行结果，甚至还可以取消任务。
Future使用示例
摘自JDK中Future示例代码
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class ArchiveSearcherImpl implements ArchiveSearcher{ @Override public String search(String target) { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } return target; }}interface ArchiveSearcher { String search(String target);}class App { public static void main(String[] args) throws InterruptedException { App app = new App(); app.showSearch("search"); } ExecutorService executor = Executors.newSingleThreadExecutor(); ArchiveSearcher searcher = new ArchiveSearcherImpl(); void showSearch(final String target) throws InterruptedException { // 提交任务 Future<String> future = executor.submit(new Callable<String>() { public String call() { return searcher.search(target); } }); displayOtherThings(); // do other things while searching try { // 拿任务执行结果 displayText(future.get()); // use future } catch (ExecutionException ex) { //cleanup(); return; } } private void displayOtherThings() { System.out.println("do other things"); } private void displayText(String s) { System.out.println(s); }} |
注意：future.get()方法是阻塞式的，如果调用该方法的时候任务尚未执行完成，则会一直等待下去，直到任务执行结束。
ExecutorService还有一个sumbit方法比较特殊：<T> Future<T> submit(Runnable task, T result);这个方法可以先把result这个参数传给task使用，然后再通过get方法把result返回。
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public class FutureTest { public static void main(String[] args) throws ExecutionException, InterruptedException { ExecutorService executor = Executors.newSingleThreadExecutor(); MyResult myResult = new MyResult(); MyTask myTask = new MyTask(myResult); // 提交任务后，在任务中操作myResult Future<MyResult> future = executor.submit(myTask, myResult); // 最后get方法可以拿到myResult System.out.println(future.get()); }}class MyTask implements Runnable { private MyResult myResult; public MyTask(MyResult myResult) { this.myResult = myResult; } @Override public void run() { myResult.setCode("10000"); }}@Data@ToStringclass MyResult { private String code;} |
FutureTask
FutureTask是一个实现了Runnable和Future接口的工具类，结合了这两个接口的能力，FutureTask即可以提交给线程任务执行，又可以获取到执行结果。
具体代码示例：
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import java.util.concurrent.*;public class FutureTaskTest { public static void main(String[] args) throws ExecutionException, InterruptedException { FutureTask<String> futureTask1 = new FutureTask<>(new MyTask1()); FutureTask<String> futureTask2 = new FutureTask<>(new MyTask2()); ExecutorService executorService = Executors.newFixedThreadPool(2); executorService.submit(futureTask1); executorService.submit(futureTask2); long start = System.currentTimeMillis(); System.out.println(futureTask1.get()); System.out.println(futureTask2.get()); long end = System.currentTimeMillis(); System.out.println(end - start); }}class MyTask2 implements Callable<String> { @Override public String call() { try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } return "MyTask2 over"; }}class MyTask1 implements Callable<String> { @Override public String call() { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } return "MyTask1 over"; }} |
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原文链接：https://blog.csdn.net/CSDN_WYL2016/article/details/125093947
