Java中的Runnable、Callable、Future、FutureTask的区别

@FunctionalInterfacepublic interface Runnable {
/**
* When an object implementing interface <code>Runnable</code> is used
* to create a thread, starting the thread causes the object's
* <code>run</code> method to be called in that separately executing
* thread.
* <p>
* The general contract of the method <code>run</code> is that it may
* take any action whatsoever.
*
* @see     java.lang.Thread#run()
*/
public abstract void run();
}

@FunctionalInterfacepublic interface Callable<V> {
 /**
* Computes a result, or throws an exception if unable to do so.
*
* @return computed result
* @throws Exception if unable to compute a result
*/
 V call() throws Exception;
}

* @see FutureTask
* @see Executor
* @since 1.5
* @author Doug Lea
* @param <V> 
 The result type returned by this Future's    {@code    get} method
*/
public interface Future<V> {/**
* Attempts to cancel execution of this task.  This attempt will
* fail if the task has already completed, has already been cancelled,
* or could not be cancelled for some other reason. If successful,
* and this task has not started when {@code cancel} is called,
* this task should never run.  If the task has already started,
* then the {@code mayInterruptIfRunning} parameter determines
* whether the thread executing this task should be interrupted in
* an attempt to stop the task.
*
* <p>After this method returns, subsequent calls to {@link #isDone} will
* always return {@code true}.  Subsequent calls to {@link #isCancelled}
* will always return {@code true} if this method returned {@code true}.
*
* @param mayInterruptIfRunning {@code true} if the thread executing this
* task should be interrupted; otherwise, in-progress tasks are allowed
* to complete
* @return {@code false} if the task could not be cancelled,
* typically because it has already completed normally;
* {@code true} otherwise
*/
 
 boolean cancel(boolean mayInterruptIfRunning);
/**
* Returns {@code true} if this task was cancelled before it completed
* normally.
*
* @return {@code true} if this task was cancelled before it completed
*/boolean isCancelled();/**
* Returns {@code true} if this task completed.
*
* Completion may be due to normal termination, an exception, or
* cancellation -- in all of these cases, this method will return
* {@code true}.
*
* @return {@code true} if this task completed
*/

boolean isDone();
/**
* Waits if necessary for the computation to complete, and then
* retrieves its result.
*
* @return the computed result
* @throws CancellationException if the computation was cancelled
* @throws ExecutionException if the computation threw an
* exception
* @throws InterruptedException if the current thread was interrupted
* while waiting
*/

 V get() throws InterruptedException, ExecutionException;
/**
* Waits if necessary for at most the given time for the computation
* to complete, and then retrieves its result, if available.
*
* @param timeout the maximum time to wait
* @param unit the time unit of the timeout argument
* @return the computed result
* @throws CancellationException if the computation was cancelled
* @throws ExecutionException if the computation threw an
* exception
* @throws InterruptedException if the current thread was interrupted
* while waiting
* @throws TimeoutException if the wait timed out
*/
 
 V get(long timeout, TimeUnit unit)   
   throws InterruptedException, ExecutionException, TimeoutException;
}

public class FutureTask<V> implements RunnableFuture<V> {

......
}

* A {@link Future} that is {@link Runnable}. Successful    
* execution of
* the {@code run} method causes completion of the {@code   Future}
* and allows access to its results.
* @see FutureTask* @see Executor* @since 1.6* 
   @author Doug Lea* @param <V> 
 The result type returned by this Future's {@code get} method
*/
public interface RunnableFuture<V> extends Runnable, Future<V> {

 /**
* Sets this Future to the result of its computation
* unless it has been cancelled.
 */
void run();
}

/**
* Creates a {@code FutureTask} that will, 
 *upon running, execute the
* given {@code Callable}.
*
* @param  callable the callable task
* @throws NullPointerException if the callable is null
*/public FutureTask(Callable<V> callable) {    
    if (callable == null)       
     throw new NullPointerException();    
     this.callable = callable;    
     this.state = NEW;       
     // ensure visibility of callable
 
  }
 /**
* Creates a {@code FutureTask} that will, upon running, execute the
* given {@code Runnable}, and arrange that {@code get} will return the
* given result on successful completion.
*
* @param runnable the runnable task
* @param result the result to return on successful completion. If
* you don't need a particular result, consider using
* constructions of the form:
* {@code Future<?> f = new FutureTask<Void>(runnable, null)}
* @throws NullPointerException if the runnable is null
*/public FutureTask(Runnable runnable, V result) {   
    this.callable = Executors.callable(runnable, result);    
    this.state = NEW;       
    // ensure visibility of callable

}

/**
* Returns a {@link Callable} object that, when
* called, runs the given task and returns the given result.  This
* can be useful when applying methods requiring a
* {@code Callable} to an otherwise resultless action.
* @param task the task to run
* @param result the result to return
* @param <T> the type of the result
* @return a callable object
* @throws NullPointerException if task null
*/
 
public static <T> Callable<T> callable(Runnable task, T result) {   
    if (task == null)        
    throw new NullPointerException();    
    return new RunnableAdapter<T>(task, result);
}

/**
* A callable that runs given task and returns given result
*/static final class RunnableAdapter<T> implements Callable<T> {    
   final Runnable task;    
   final T result;
   RunnableAdapter(Runnable task, T result) {        
     this.task = task;        
     this.result = result;
   }   
    public T call() {
       task.run();        
        return result;
   }
}

public static class Task implements Runnable {   @Override    public void run() {       
  // TODO Auto-generated method stub
       System.out.println("run");
   }}
public static class Task2 implements Callable<Integer> {   @Override    
     public Integer call() throws Exception {
       System.out.println("call");        
        return fibc(30);
   }} /**
* runnable, 无返回值
*/  public static void testRunnable(){
   ExecutorService executorService = Executors.newCachedThreadPool();   Future<String> future = 
      (Future<String>) executorService.submit(new Task());    
   try {
       System.out.println(future.get());
   } catch (InterruptedException e) {        
       // TODO Auto-generated catch block
       e.printStackTrace();
   } catch (ExecutionException e) {        
    // TODO Auto-generated catch block
       e.printStackTrace();
   }   executorService.shutdown();
}
 /**
* Callable, 有返回值
*/  
 public static void testCallable(){
   ExecutorService executorService = Executors.newCachedThreadPool();   Future<Integer> future = 
      (Future<Integer>) executorService.submit(new Task2());    
try {
       System.out.println(future.get());
   } catch (InterruptedException e) {        
    // TODO Auto-generated catch block
       e.printStackTrace();
   } catch (ExecutionException e) {       
    // TODO Auto-generated catch block
       e.printStackTrace();
    }    executorService.shutdown();
  }
 /**
* FutureTask则是一个RunnableFuture<V>，
 * 即实现了Runnbale又实现了Futrue<V>这两个接口，
* 另外它还可以包装Runnable(实际上会转换为Callable)和Callable
* <V>，所以一般来讲是一个符合体了，它可以通过Thread包装来直接执行，
 * 也可以提交给ExecuteService来执行
* ，并且还可以通过v get()返回执行结果，
 *  在线程体没有执行完成的时候，主线程一直阻塞等待，执行完则直接返回结果。
*/  public static void testFutureTask(){
   ExecutorService executorService = 
            Executors.newCachedThreadPool();
   FutureTask<Integer> futureTask = 
             new FutureTask<Integer>(new Task2());   executorService.submit(futureTask);    try {
       System.out.println(futureTask.get());
   } catch (InterruptedException e) {        
      // TODO Auto-generated catch block
       e.printStackTrace();
   } catch (ExecutionException e) {        
      // TODO Auto-generated catch block
       e.printStackTrace();
   }   executorService.shutdown();
} /**
* FutureTask则是一个RunnableFuture<V>，
   即实现了Runnbale又实现了Futrue<V>这两个接口，
* 另外它还可以包装Runnable(实际上会转换为Callable)和Callable
* <V>，所以一般来讲是一个符合体了，它可以通过Thread包装来直接执行，
    也可以提交给ExecuteService来执行
* ，并且还可以通过v get()返回执行结果，在线程体没有执行完成的时候，
    主线程一直阻塞等待，执行完则直接返回结果。
*/  public static void testFutureTask2(){
   ExecutorService executorService = Executors.newCachedThreadPool();
   FutureTask<Integer> futureTask = 
       new FutureTask<Integer>(new Runnable() {       @Override        public void run() {           
       // TODO Auto-generated method stub
           System.out.println("testFutureTask2 run");
       }
   },fibc(30));   executorService.submit(futureTask);    try {
       System.out.println(futureTask.get());
   } catch (InterruptedException e) {        
   // TODO Auto-generated catch block
       e.printStackTrace();
   } catch (ExecutionException e) {        
    // TODO Auto-generated catch block
       e.printStackTrace();
   }   executorService.shutdown();
}public static void main(String[] args) {   testCallable();}/**
* 效率低下的斐波那契数列, 耗时的操作
*  
* @param num
* @return
*/   static int fibc(int num) {  
    if (num == 0) {  
       return 0;  
    }  
    if (num == 1) {  
       return 1;  
    }  
    return fibc(num - 1) + fibc(num - 2);  
}  }