标签：style blog http color os java io strong ar
从java5开始，java提供了Callable接口，Callable接口提供了一个call方法可以作为线程的执行体，但call方法比run方法功能更加强大。主要体现在：示例代码：
Callable<Integer> c = new Callable<Integer>()
{
@Override
public Integer call() throws Exception
{
System.out.println("running...");
Thread.sleep(2000);
return 215;
}
};
FutureTask<Integer> task = new FutureTask<>(c);
new Thread(task).start();
try
{
System.out.println("result : "+task.get());
}
catch (InterruptedException e)
{
e.printStackTrace();
}
catch (ExecutionException e)
{
e.printStackTrace();
}
}public interface Callable<V> {
V call() throws Exception;
}
Runnable接口大家都很熟悉，那么这个Future接口提供了什么样的方法呢？
public interface Future<V> {
boolean cancel(boolean mayInterruptIfRunning);//取消Future里面关联的call方法
boolean isCancelled();//任务是否取消
boolean isDone();//任务是否完成
V get() throws InterruptedException, ExecutionException;//获取call方法的结果
V get(long timeout, TimeUnit unit)//设置超时时间，超过此时间未收到结果将抛出异常
throws InterruptedException, ExecutionException, TimeoutException;
} @Override
public void run() {
if (target != null) {
target.run();
}
}即判断是否传入了Runnable类型的target，如果有，将会执行Runnable的run方法，这里我们传入的是FutureTask，所以会调用FutureTask类的run方法： public void run() {
sync.innerRun();
}void innerRun() {
if (!compareAndSetState(READY, RUNNING))
return;
runner = Thread.currentThread();
if (getState() == RUNNING) { // recheck after setting thread
V result;
try {
result = callable.call();//调用的是callable的call方法
} catch (Throwable ex) {
setException(ex);
return;
}
set(result);
} else {
releaseShared(0); // cancel
}
}
public V get() throws InterruptedException, ExecutionException {
return sync.innerGet();
} V innerGet() throws InterruptedException, ExecutionException {
acquireSharedInterruptibly(0);
if (getState() == CANCELLED)
throw new CancellationException();
if (exception != null)
throw new ExecutionException(exception);
return result;
}返回了result变量。
标签：style blog http color os java io strong ar
原文地址：http://blog.csdn.net/chdjj/article/details/38900521
