Package com.google.common.util.concurrent

com.google.common.util.concurrent 是 Google Guava 库中的一个包。Guava 是 Google 的一个开源 Java 库，提供了很多实用的工具类和方法，以增强 Java 的标准库。
具体到 com.google.common.util.concurrent 这个包，它主要包含了一些与并发和异步处理相关的工具和类。例如：

1. ListenableFuture: 表示异步计算的结果。它允许你注册回调来处理计算完成或失败的情况。
2. ListeningExecutorService 和 ListeningScheduledExecutorService: 这些是执行器和调度执行器的包装器，它们自动为任务执行和调度任务提供 ListenableFuture。
3. ListenableFutureTask: 这是一个将 Runnable 或 Callable 与 ListenableFuture 结合的类。
4. Futures: 提供了一些静态方法来操作 ListenableFuture，例如组合、转换或忽略多个未来的结果。
5. Transformers: 用于自定义如何转换 ListenableFuture 的结果。
6. Helpers: 一些实用方法，用于处理常见的并发和异步任务。
   使用 Guava 的并发工具可以更轻松地处理并发和异步任务，而不需要编写大量的低级代码。当然可以，以下是一些建议，供您参考：
7. RateLimiter: 用于限制在特定时间段内可以执行的操作的数量。这对于防止系统过载非常有用。
8. Semaphore: 类似于传统的信号量，用于限制对资源的并发访问。
9. CountDownLatch: 允许一个或多个线程等待其他线程完成一系列操作。
10. CyclicBarrier: 允许一组线程互相等待，直到所有线程都达到某个状态。
    这些类和工具可以帮助你更有效地处理并发和异步任务，提高你的代码的可读性和可维护性。在使用这些工具时，请务必仔细阅读文档，以确保你了解每个工具的正确用法和适用场景。除了上述提到的工具，com.google.common.util.concurrent包还包含了一些其他的类和接口，这些可以用来解决常见的并发问题。以下是一些更详细的介绍：
11. ExecutorService：这是一个用于执行任务的接口，可以提交Runnable或Callable对象来执行。你可以使用线程池作为ExecutorService的实现，以便有效地管理线程。
12. ScheduledExecutorService：这是一个可以定期执行任务的ExecutorService。你可以使用它来定期执行任务，例如定时器或周期性任务。
13. AbstractExecutorService：这是一个ExecutorService的抽象实现，它提供了执行任务和关闭ExecutorService的基本实现。你可以通过扩展这个类来创建自己的ExecutorService实现。
14. ThreadPoolExecutor：这是一个基于线程池的ExecutorService实现。你可以使用它来创建具有固定线程池大小的ExecutorService，或者使用带有可调整线程池大小的自定义配置。
    这些类和接口可以帮助你更好地管理并发任务，并确保你的应用程序能够高效地利用系统资源。在使用这些工具时，请注意线程安全问题，并确保你的代码在并发环境中正确地工作。当然，以下是一些使用这些工具的示例代码：

// 使用线程池执行任务
ExecutorService executor = Executors.newFixedThreadPool(10);
executor.submit(() -> {
    // 执行任务的代码
});
executor.shutdown(); // 关闭线程池
// 使用定时器执行任务
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(() -> {
    // 定期执行任务的代码
}, 0, 5, TimeUnit.SECONDS); // 首次执行延迟0秒，之后每5秒执行一次
scheduler.shutdown(); // 关闭调度器
// 使用RateLimiter限制任务执行速率
RateLimiter rateLimiter = RateLimiter.create(5.0); // 每秒最多执行5个任务
rateLimiter.acquire(); // 获取一个令牌，如果当前速率达到上限，则阻塞直到获取到令牌
// 使用Semaphore限制并发任务数量
Semaphore semaphore = new Semaphore(3); // 最多允许3个任务同时执行
semaphore.acquire(); // 获取一个许可，如果当前许可数量已满，则阻塞直到获取到许可
// 执行任务的代码
semaphore.release(); // 释放一个许可，允许其他任务开始执行

这些示例代码展示了如何使用Guava提供的并发工具来管理并发任务，确保你的代码能够高效地运行并处理多个任务。记得在使用这些工具时注意线程安全问题，并确保你的代码在并发环境中正确地工作。当然，除了上述提到的工具，还有一些其他的工具和类可以帮助你更好地处理并发和异步任务。以下是一些更详细的介绍：
15. Future：这是一个表示异步计算结果的接口。你可以使用Future来获取异步计算的结果，或者检查计算是否完成。
16. ListenableFuture：这是一个表示可响应的异步计算结果的接口。你可以将一个ListenableFuture注册到一个回调监听器上，以便在计算完成时自动执行回调函数。
17. FutureTask：这是一个实现了Future接口的类。你可以使用FutureTask来包装一个Runnable或Callable对象，以便将其提交给ExecutorService执行，并获取Future对象来获取结果。
18. ListeningExecutorService：这是一个执行Callable或Runnable对象的ExecutorService，它返回一个ListenableFuture对象作为结果。你可以使用ListeningExecutorService来执行异步任务，并注册回调监听器来处理结果。
这些工具和类可以帮助你更好地处理并发和异步任务，并确保你的代码能够高效地运行。在使用这些工具时，请注意线程安全问题，并确保你的代码在并发环境中正确地工作。同时，记得根据实际情况选择合适的并发工具和类，并仔细阅读文档以了解它们的用法和适用场景。
Concurrency utilities.

See:
Description

Interface Summary
CheckedFuture<V,X extends Exception> A CheckedFuture is a ListenableFuture that includes versions of the get methods that can throw a checked exception.
FutureCallback A callback for accepting the results of a Future computation asynchronously.
ListenableFuture A Future that accepts completion listeners.
ListeningExecutorService An ExecutorService that returns ListenableFuture instances.
ListeningScheduledExecutorService A ScheduledExecutorService that returns ListenableFuture instances from its ExecutorService methods.
Service An object with an operational state, plus asynchronous Service.start() and Service.stop() lifecycle methods to transfer into and out of this state.
TimeLimiter Produces proxies that impose a time limit on method calls to the proxied object.
UninterruptibleFuture Deprecated. Use getUninterruptibly.

Class Summary
AbstractCheckedFuture<V,X extends Exception> A delegating wrapper around a ListenableFuture that adds support for the AbstractCheckedFuture.checkedGet() and AbstractCheckedFuture.checkedGet(long, TimeUnit) methods.
AbstractExecutionThreadService Base class for services that can implement AbstractExecutionThreadService.startUp(), AbstractExecutionThreadService.run() and AbstractExecutionThreadService.shutDown() methods.
AbstractFuture An abstract implementation of the ListenableFuture interface.
AbstractIdleService Base class for services that do not need a thread while “running” but may need one during startup and shutdown.
AbstractListenableFuture Deprecated. Use AbstractFuture.
AbstractService Base class for implementing services that can handle AbstractService.doStart() and AbstractService.doStop() requests, responding to them with AbstractService.notifyStarted() and AbstractService.notifyStopped() callbacks.
Atomics Static utility methods pertaining to classes in the java.util.concurrent.atomic package.
Callables Static utility methods pertaining to the Callable interface.
ExecutionList A list of listeners, each with an associated Executor, that guarantees that every Runnable that is added will be executed after ExecutionList.execute() is called.
FakeTimeLimiter A TimeLimiter implementation which actually does not attempt to limit time at all.
ForwardingBlockingQueue A BlockingQueue which forwards all its method calls to another BlockingQueue.
ForwardingCheckedFuture<V,X extends Exception> A future which forwards all its method calls to another future.
ForwardingCheckedFuture.SimpleForwardingCheckedFuture<V,X extends Exception> A simplified version of ForwardingCheckedFuture where subclasses can pass in an already constructed CheckedFuture as the delegate.
ForwardingExecutorService An executor service which forwards all its method calls to another executor service.
ForwardingFuture A ForwardingFuture.SimpleForwardingFuture which forwards all its method calls to another future.
ForwardingFuture.SimpleForwardingFuture A simplified version of ForwardingFuture where subclasses can pass in an already constructed Future as the delegate.
ForwardingListenableFuture A ForwardingListenableFuture.SimpleForwardingListenableFuture which forwards all its method calls to another future.
ForwardingListenableFuture.SimpleForwardingListenableFuture A simplified version of ForwardingListenableFuture where subclasses can pass in an already constructed ListenableFuture as the delegate.
ForwardingListeningExecutorService A listening executor service which forwards all its method calls to another listening executor service.
ForwardingService A Service that forwards all method calls to another service.
Futures Static utility methods pertaining to the Future interface.
JdkFutureAdapters Utilities necessary for working with libraries that supply plain Future instances.
ListenableFutureTask A FutureTask that also implements the ListenableFuture interface.
Monitor A synchronization abstraction supporting waiting on arbitrary boolean conditions.
Monitor.Guard A boolean condition for which a thread may wait.
MoreExecutors Factory and utility methods for Executor, ExecutorService, and ThreadFactory.
SettableFuture A ListenableFuture whose result may be set by a SettableFuture.set(Object) or SettableFuture.setException(Throwable) call.
SimpleTimeLimiter A TimeLimiter that runs method calls in the background using an ExecutorService.
ThreadFactoryBuilder A ThreadFactory builder, providing any combination of these features: whether threads should be marked as daemon threads a naming format a thread priority an uncaught exception handler a backing thread factory If no backing thread factory is provided, a default backing thread factory is used as if by calling setThreadFactory(Executors.defaultThreadFactory()).
UncaughtExceptionHandlers Factories for Thread.UncaughtExceptionHandler instances.
Uninterruptibles Utilities for treating interruptible operations as uninterruptible.

Enum Summary
Service.State The lifecycle states of a service.

Exception Summary
UncheckedExecutionException Unchecked variant of ExecutionException.
UncheckedTimeoutException Unchecked version of TimeoutException.

Error Summary
ExecutionError Error variant of ExecutionException.

Package com.google.common.util.concurrent Description

Concurrency utilities.

Commonly used types include ListenableFuture and Service.

Commonly used utilities include Futures, MoreExecutors, and ThreadFactoryBuilder.

This package is a part of the open-source Guava libraries.