Runnable、Callable、Future和FutureTask
线程池:
继承关系:ThreadPoolExecutor->ExecutorService->Executor
Executors:ThreadPoolExecutor的工厂类,生成不同的线程池
主要关系:在线程池中:
<T> Future<T> submit(Callable<T> task);
<T> Future<T> submit(Runnable task, T result);
Future<?> submit(Runnable task);
Callable:
位于java.util.concurrent包下,类似于Runnable:
public interface Callable<V> {
V call() throws Exception;
}
Future类:
位于java.util.concurrent包下
Future就是对于具体的Runnable或者Callable任务的执行结果进行取消、查询是否完成、获取结果。
必要时可以通过get方法获取执行结果,该方法会阻塞直到任务返回结果。
public interface Future<V> {
boolean cancel(boolean mayInterruptIfRunning);
boolean isCancelled();
boolean isDone();
V get() throws InterruptedException, ExecutionException;
V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
}
FutureTask:
FutureTask是Future的实现类,用来实现真正的Future工作,用来对Callable或者Runbale的任务实现监控:
构造方法:
注意第二个,因为Runnable无返回值,所以要手动提前写一个结果,当Runnable执行完毕返回这个值,当然不关心返回值的话传null
public FutureTask(Callable<V> callable) {
}
public FutureTask(Runnable runnable, V result) {
}
线程池继承关系:
继承关系:ThreadPoolExecutor->ExecutorService->Executor
Executors:ThreadPoolExecutor的工厂类,生成不同的线程池
public interface Executor {
void execute(Runnable command);
}
public interface ExecutorService extends Executor {
void shutdown();
List<Runnable> shutdownNow();
boolean isShutdown();
boolean isTerminated();
boolean awaitTermination(long timeout, TimeUnit unit)
throws InterruptedException;
<T> Future<T> submit(Callable<T> task);
<T> Future<T> submit(Runnable task, T result);
Future<?> submit(Runnable task);
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
throws InterruptedException;
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
long timeout, TimeUnit unit)
throws InterruptedException;
<T> T invokeAny(Collection<? extends Callable<T>> tasks)
throws InterruptedException, ExecutionException;
<T> T invokeAny(Collection<? extends Callable<T>> tasks,
long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException;
}