/** 
* @see FutureTask 
 * @see Executor 
 * @since 1.5 
 * @author Doug Lea 
 * @param <V> The result type returned by this Future's <tt>get</tt> 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 <tt>cancel</tt> is called, 
     * this task should never run.  If the task has already started, 
     * then the <tt>mayInterruptIfRunning</tt> parameter determines 
     * whether the thread executing this task should be interrupted in 
     * an attempt to stop the task.     * 
     */  
    boolean cancel(boolean mayInterruptIfRunning);  
    /** 
     * Returns <tt>true</tt> if this task was cancelled before it completed 
     * normally. 
     */  
    boolean isCancelled();  
    /** 
     * Returns <tt>true</tt> if this task completed. 
     * 
     */  
    boolean isDone();  
    /** 
     * Waits if necessary for the computation to complete, and then 
     * retrieves its result. 
     * 
     * @return the computed result 
     */  
    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 
     */  
    V get(long timeout, TimeUnit unit)  
        throws InterruptedException, ExecutionException, TimeoutException;  
}  

public class FutureTask<V> implements RunnableFuture<V>

public interface RunnableFuture<V> extends Runnable, Future<V> {  
    /** 
     * Sets this Future to the result of its computation 
     * unless it has been cancelled. 
     */  
    void run();  
}  

public FutureTask(Callable<V> callable) {  
    if (callable == null)  
        throw new NullPointerException();  
    this.callable = callable;  
    this.state = NEW;       // ensure visibility of callable  
}  
public FutureTask(Runnable runnable, V result) {  
    this.callable = Executors.callable(runnable, result);  
    this.state = NEW;       // ensure visibility of callable  
}  

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 class Test {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newCachedThreadPool();
        Task task = new Task();
        Future<Integer> result = executor.submit(task);
        executor.shutdown();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
        System.out.println("主線程在執(zhí)行任務");
        try {
            System.out.println("task運行結果"+result.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        System.out.println("所有任務執(zhí)行完畢");
    }
}
class Task implements Callable<Integer>{
    @Override
    public Integer call() throws Exception {
        System.out.println("子線程在進行計算");
        Thread.sleep(3000);
        int sum = 0;
        for(int i=0;i<100;i++)
            sum += i;
        return sum;
    }
}

public class Test {
    public static void main(String[] args) {
        //第一種方式
        ExecutorService executor = Executors.newCachedThreadPool();
        Task task = new Task();
        FutureTask<Integer> futureTask = new FutureTask<Integer>(task);
        executor.submit(futureTask);
        executor.shutdown();
        //第二種方式，注意這種方式和第一種方式效果是類似的，只不過一個使用的是ExecutorService，一個使用的是Thread
        /*Task task = new Task();
        FutureTask<Integer> futureTask = new FutureTask<Integer>(task);
        Thread thread = new Thread(futureTask);
        thread.start();*/
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
        System.out.println("主線程在執(zhí)行任務");
        try {
            System.out.println("task運行結果"+futureTask.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        System.out.println("所有任務執(zhí)行完畢");
    }
}
class Task implements Callable<Integer>{
    @Override
    public Integer call() throws Exception {
        System.out.println("子線程在進行計算");
        Thread.sleep(3000);
        int sum = 0;
        for(int i=0;i<100;i++)
            sum += i;
        return sum;
    }
}