java concurrent Callable
实现Callable接口的类其实就是一个任务，可以异步执行并返回结果。
通过ExecutorService.submit 方法提交一个callable任务，并且通过Future对象来获得结果。
Future对象可以取消运行任务，设置等待时间，获取任务状态，最终获得任务结果。
1 public static void main(String[] args) {
2 ExecutorService exec = Executors.newCachedThreadPool();
3
4 Future<String> future = exec.submit(new CallableThread(0));
5
6 try {
7 System.out.println("Got it: " + future.get(1000, TimeUnit.SECONDS));
8 } catch (InterruptedException e) {
9 e.printStackTrace();
10 } catch (ExecutionException e) {
11 e.printStackTrace();
12 } catch (TimeoutException e) {
13 e.printStackTrace();
14 }finally{
15 exec.shutdown();
16 }
17 }
1 public class CallableThread implements Callable<String> {
2
3 private int count = 0;
4
5 public CallableThread(int count){
6 this.count = count;
7 }
8
9 public String call() throws Exception {
10 doSomething();
11 return "Thread Name: " + Thread.currentThread().getName() + " , count: " + count;
12 }
13
14 private void doSomething(){
15 while(count < 5){
16 count++;
17 System.out.println("Thread Name: " + Thread.currentThread().getName() + " , count: " + count);
18 try {
19 Thread.sleep(1000);
20 } catch (InterruptedException e) {
21 e.printStackTrace();
22 }
23 }
24 }
25
26 }
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