ExecutorService.submit()会返回一个future.
blic static void main(String[] args) {
ExecutorService threadPool = Executors.newSingleThreadExecutor();
Future future =
threadPool.submit(
new Callable<String>() {
public String call() throws Exception{
Thread.sleep(2000);
return "hello";
};
}
);
System.out.println("等待结果");
try {
System.out.println("等待结果"+future.get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
运行结果：
等待结果
等待结果hello
而如果使用CompletionService.submit方法，会在多个任务运行时，按照完成的先后顺序依次返回，看代码：
ExecutorService threadPool2 = Executors.newFixedThreadPool(10);
CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);
for(int i=0;i<10;++i){
final int seq = i;
completionService.submit(new Callable<Integer>() {
@Override
public Integer call() throws Exception {
Thread.sleep(new Random().nextInt(5000));
return seq;
}
});
}
for(int i=0;i<10;++i){
try {
System.out.println(completionService.take().get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
运行结果：
2
8
0
1
5
3
6
7
4
9