关于ExecutorService中的execute()和submit()方法的区别

ExecutorService中的execute()和submit()方法的区别

先看源码

/* * @(#)ExecutorService.java1.14 06/07/14 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */package java.util.concurrent;import java.util.List;import java.util.Collection;import java.security.PrivilegedAction;import java.security.PrivilegedExceptionAction;/** * An {@link Executor} that provides methods to manage termination and * methods that can produce a {@link Future} for tracking progress of * one or more asynchronous tasks. * * <p> An <tt>ExecutorService</tt> can be shut down, which will cause * it to reject new tasks.  Two different methods are provided for * shutting down an <tt>ExecutorService</tt>. The {@link #shutdown} * method will allow previously submitted tasks to execute before * terminating, while the {@link #shutdownNow} method prevents waiting * tasks from starting and attempts to stop currently executing tasks. * Upon termination, an executor has no tasks actively executing, no * tasks awaiting execution, and no new tasks can be submitted.  An * unused <tt>ExecutorService</tt> should be shut down to allow * reclamation of its resources. * * <p> Method <tt>submit</tt> extends base method {@link * Executor#execute} by creating and returning a {@link Future} that * can be used to cancel execution and/or wait for completion. * Methods <tt>invokeAny</tt> and <tt>invokeAll</tt> perform the most * commonly useful forms of bulk execution, executing a collection of * tasks and then waiting for at least one, or all, to * complete. (Class {@link ExecutorCompletionService} can be used to * write customized variants of these methods.) * * <p>The {@link Executors} class provides factory methods for the * executor services provided in this package. * * <h3>Usage Examples</h3> * * Here is a sketch of a network service in which threads in a thread * pool service incoming requests. It uses the preconfigured {@link * Executors#newFixedThreadPool} factory method: * * <pre> * class NetworkService implements Runnable { *   private final ServerSocket serverSocket; *   private final ExecutorService pool; * *   public NetworkService(int port, int poolSize) *       throws IOException { *     serverSocket = new ServerSocket(port); *     pool = Executors.newFixedThreadPool(poolSize); *   } * *   public void run() { // run the service *     try { *       for (;;) { *         pool.execute(new Handler(serverSocket.accept())); *       } *     } catch (IOException ex) { *       pool.shutdown(); *     } *   } * } * * class Handler implements Runnable { *   private final Socket socket; *   Handler(Socket socket) { this.socket = socket; } *   public void run() { *     // read and service request on socket *   } * } * </pre> * * The following method shuts down an <tt>ExecutorService</tt> in two phases, * first by calling <tt>shutdown</tt> to reject incoming tasks, and then * calling <tt>shutdownNow</tt>, if necessary, to cancel any lingering tasks: * * <pre> * void shutdownAndAwaitTermination(ExecutorService pool) { *   pool.shutdown(); // Disable new tasks from being submitted *   try { *     // Wait a while for existing tasks to terminate *     if (!pool.awaitTermination(60, TimeUnit.SECONDS)) { *       pool.shutdownNow(); // Cancel currently executing tasks *       // Wait a while for tasks to respond to being cancelled *       if (!pool.awaitTermination(60, TimeUnit.SECONDS)) *           System.err.println("Pool did not terminate"); *     } *   } catch (InterruptedException ie) { *     // (Re-)Cancel if current thread also interrupted *     pool.shutdownNow(); *     // Preserve interrupt status *     Thread.currentThread().interrupt(); *   } * } * </pre> * * <p>Memory consistency effects: Actions in a thread prior to the * submission of a {@code Runnable} or {@code Callable} task to an * {@code ExecutorService} * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> * any actions taken by that task, which in turn <i>happen-before</i> the * result is retrieved via {@code Future.get()}. * * @since 1.5 * @author Doug Lea */public interface ExecutorService extends Executor {    /**     * Initiates an orderly shutdown in which previously submitted     * tasks are executed, but no new tasks will be accepted.     * Invocation has no additional effect if already shut down.     *     * @throws SecurityException if a security manager exists and     *         shutting down this ExecutorService may manipulate     *         threads that the caller is not permitted to modify     *         because it does not hold {@link     *         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,     *         or the security manager's <tt>checkAccess</tt> method     *         denies access.     */    void shutdown();    /**     * Attempts to stop all actively executing tasks, halts the     * processing of waiting tasks, and returns a list of the tasks that were     * awaiting execution.     *     * <p>There are no guarantees beyond best-effort attempts to stop     * processing actively executing tasks.  For example, typical     * implementations will cancel via {@link Thread#interrupt}, so any     * task that fails to respond to interrupts may never terminate.     *     * @return list of tasks that never commenced execution     * @throws SecurityException if a security manager exists and     *         shutting down this ExecutorService may manipulate     *         threads that the caller is not permitted to modify     *         because it does not hold {@link     *         java.lang.RuntimePermission}<tt>("modifyThread")</tt>,     *         or the security manager's <tt>checkAccess</tt> method     *         denies access.     */    List<Runnable> shutdownNow();    /**     * Returns <tt>true</tt> if this executor has been shut down.     *     * @return <tt>true</tt> if this executor has been shut down     */    boolean isShutdown();    /**     * Returns <tt>true</tt> if all tasks have completed following shut down.     * Note that <tt>isTerminated</tt> is never <tt>true</tt> unless     * either <tt>shutdown</tt> or <tt>shutdownNow</tt> was called first.     *     * @return <tt>true</tt> if all tasks have completed following shut down     */    boolean isTerminated();    /**     * Blocks until all tasks have completed execution after a shutdown     * request, or the timeout occurs, or the current thread is     * interrupted, whichever happens first.     *     * @param timeout the maximum time to wait     * @param unit the time unit of the timeout argument     * @return <tt>true</tt> if this executor terminated and     *         <tt>false</tt> if the timeout elapsed before termination     * @throws InterruptedException if interrupted while waiting     */    boolean awaitTermination(long timeout, TimeUnit unit)        throws InterruptedException;    /**     * Submits a value-returning task for execution and returns a     * Future representing the pending results of the task. The     * Future's <tt>get</tt> method will return the task's result upon     * successful completion.     *     * <p>     * If you would like to immediately block waiting     * for a task, you can use constructions of the form     * <tt>result = exec.submit(aCallable).get();</tt>     *     * <p> Note: The {@link Executors} class includes a set of methods     * that can convert some other common closure-like objects,     * for example, {@link java.security.PrivilegedAction} to     * {@link Callable} form so they can be submitted.     *     * @param task the task to submit     * @return a Future representing pending completion of the task     * @throws RejectedExecutionException if the task cannot be     *         scheduled for execution     * @throws NullPointerException if the task is null     */    <T> Future<T> submit(Callable<T> task);    /**     * Submits a Runnable task for execution and returns a Future     * representing that task. The Future's <tt>get</tt> method will     * return the given result upon successful completion.     *     * @param task the task to submit     * @param result the result to return     * @return a Future representing pending completion of the task     * @throws RejectedExecutionException if the task cannot be     *         scheduled for execution     * @throws NullPointerException if the task is null     */    <T> Future<T> submit(Runnable task, T result);    /**     * Submits a Runnable task for execution and returns a Future     * representing that task. The Future's <tt>get</tt> method will     * return <tt>null</tt> upon <em>successful</em> completion.     *     * @param task the task to submit     * @return a Future representing pending completion of the task     * @throws RejectedExecutionException if the task cannot be     *         scheduled for execution     * @throws NullPointerException if the task is null     */    Future<?> submit(Runnable task);    /**     * Executes the given tasks, returning a list of Futures holding     * their status and results when all complete.     * {@link Future#isDone} is <tt>true</tt> for each     * element of the returned list.     * Note that a <em>completed</em> task could have     * terminated either normally or by throwing an exception.     * The results of this method are undefined if the given     * collection is modified while this operation is in progress.     *     * @param tasks the collection of tasks     * @return A list of Futures representing the tasks, in the same     *         sequential order as produced by the iterator for the     *         given task list, each of which has completed.     * @throws InterruptedException if interrupted while waiting, in     *         which case unfinished tasks are cancelled.     * @throws NullPointerException if tasks or any of its elements are <tt>null</tt>     * @throws RejectedExecutionException if any task cannot be     *         scheduled for execution     */    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)        throws InterruptedException;    /**     * Executes the given tasks, returning a list of Futures holding     * their status and results     * when all complete or the timeout expires, whichever happens first.     * {@link Future#isDone} is <tt>true</tt> for each     * element of the returned list.     * Upon return, tasks that have not completed are cancelled.     * Note that a <em>completed</em> task could have     * terminated either normally or by throwing an exception.     * The results of this method are undefined if the given     * collection is modified while this operation is in progress.     *     * @param tasks the collection of tasks     * @param timeout the maximum time to wait     * @param unit the time unit of the timeout argument     * @return a list of Futures representing the tasks, in the same     *         sequential order as produced by the iterator for the     *         given task list. If the operation did not time out,     *         each task will have completed. If it did time out, some     *         of these tasks will not have completed.     * @throws InterruptedException if interrupted while waiting, in     *         which case unfinished tasks are cancelled     * @throws NullPointerException if tasks, any of its elements, or     *         unit are <tt>null</tt>     * @throws RejectedExecutionException if any task cannot be scheduled     *         for execution     */    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,                                  long timeout, TimeUnit unit)        throws InterruptedException;    /**     * Executes the given tasks, returning the result     * of one that has completed successfully (i.e., without throwing     * an exception), if any do. Upon normal or exceptional return,     * tasks that have not completed are cancelled.     * The results of this method are undefined if the given     * collection is modified while this operation is in progress.     *     * @param tasks the collection of tasks     * @return the result returned by one of the tasks     * @throws InterruptedException if interrupted while waiting     * @throws NullPointerException if tasks or any of its elements     *         are <tt>null</tt>     * @throws IllegalArgumentException if tasks is empty     * @throws ExecutionException if no task successfully completes     * @throws RejectedExecutionException if tasks cannot be scheduled     *         for execution     */    <T> T invokeAny(Collection<? extends Callable<T>> tasks)        throws InterruptedException, ExecutionException;    /**     * Executes the given tasks, returning the result     * of one that has completed successfully (i.e., without throwing     * an exception), if any do before the given timeout elapses.     * Upon normal or exceptional return, tasks that have not     * completed are cancelled.     * The results of this method are undefined if the given     * collection is modified while this operation is in progress.     *     * @param tasks the collection of tasks     * @param timeout the maximum time to wait     * @param unit the time unit of the timeout argument     * @return the result returned by one of the tasks.     * @throws InterruptedException if interrupted while waiting     * @throws NullPointerException if tasks, any of its elements, or     *         unit are <tt>null</tt>     * @throws TimeoutException if the given timeout elapses before     *         any task successfully completes     * @throws ExecutionException if no task successfully completes     * @throws RejectedExecutionException if tasks cannot be scheduled     *         for execution     */    <T> T invokeAny(Collection<? extends Callable<T>> tasks,                    long timeout, TimeUnit unit)        throws InterruptedException, ExecutionException, TimeoutException;}

下面是execute()：

/* * @(#)Executor.java1.9 06/01/30 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */package java.util.concurrent;/** * An object that executes submitted {@link Runnable} tasks. This * interface provides a way of decoupling task submission from the * mechanics of how each task will be run, including details of thread * use, scheduling, etc.  An <tt>Executor</tt> is normally used * instead of explicitly creating threads. For example, rather than * invoking <tt>new Thread(new(RunnableTask())).start()</tt> for each * of a set of tasks, you might use: * * <pre> * Executor executor = <em>anExecutor</em>; * executor.execute(new RunnableTask1()); * executor.execute(new RunnableTask2()); * ... * </pre> * * However, the <tt>Executor</tt> interface does not strictly * require that execution be asynchronous. In the simplest case, an * executor can run the submitted task immediately in the caller's * thread: * * <pre> * class DirectExecutor implements Executor { *     public void execute(Runnable r) { *         r.run(); *     } * }</pre> * * More typically, tasks are executed in some thread other * than the caller's thread.  The executor below spawns a new thread * for each task. * * <pre> * class ThreadPerTaskExecutor implements Executor { *     public void execute(Runnable r) { *         new Thread(r).start(); *     } * }</pre> * * Many <tt>Executor</tt> implementations impose some sort of * limitation on how and when tasks are scheduled.  The executor below * serializes the submission of tasks to a second executor, * illustrating a composite executor. * * <pre> * class SerialExecutor implements Executor { *     final Queue<Runnable> tasks = new ArrayDeque<Runnable>(); *     final Executor executor; *     Runnable active; * *     SerialExecutor(Executor executor) { *         this.executor = executor; *     } * *     public synchronized void execute(final Runnable r) { *         tasks.offer(new Runnable() { *             public void run() { *                 try { *                     r.run(); *                 } finally { *                     scheduleNext(); *                 } *             } *         }); *         if (active == null) { *             scheduleNext(); *         } *     } * *     protected synchronized void scheduleNext() { *         if ((active = tasks.poll()) != null) { *             executor.execute(active); *         } *     } * }</pre> * * The <tt>Executor</tt> implementations provided in this package * implement {@link ExecutorService}, which is a more extensive * interface.  The {@link ThreadPoolExecutor} class provides an * extensible thread pool implementation. The {@link Executors} class * provides convenient factory methods for these Executors. * * <p>Memory consistency effects: Actions in a thread prior to * submitting a {@code Runnable} object to an {@code Executor} * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> * its execution begins, perhaps in another thread. * * @since 1.5 * @author Doug Lea */public interface Executor {    /**     * Executes the given command at some time in the future.  The command     * may execute in a new thread, in a pooled thread, or in the calling     * thread, at the discretion of the <tt>Executor</tt> implementation.     *     * @param command the runnable task     * @throws RejectedExecutionException if this task cannot be     * accepted for execution.     * @throws NullPointerException if command is null     */    void execute(Runnable command);}

经源码可知，总结有以下三个区别：

1.可以看到sumbit()参数可以接受多个参数，runnable,或者是callable都可以，而execute只能接受runnable。

2.sumbit可以返回future,而execute不能(个人感觉这点最重要)

3.sumbit方便做异常处理，可以捕获future.get()中的异常来捕获异常

从上面的情况分析，sumbit的功能是强于execute，从目前我的知识系统中看，不管什么场合都用sumbit就行了

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