Executors class in java

Last Update:2014-04-04 Source: Internet

Author: User

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I. Overview

Located inJava. util. concurrent package.

TheExecutor,ExecutorService,ScheduledExecutorService,ThreadFactoryAndCallableClass factory and practical methods. This class supports the following methods:

Create and return the string with common configurations ExecutorService. Create and return the string with common configurations ScheduledExecutorService. Create and return the "encapsulated" ExecutorService method, which disables reconfiguration by making implementation-specific methods inaccessible. Create and return ThreadFactoryIt can set the newly created thread to a known state. Create and return non-closure form CallableTo use Callable. Ii. Detailed Methods

1. public static ExecutorServiceNewFixedThreadPool(Int nThreads) creates a thread pool that can reuse a fixed number of threads and runs these threads in a shared unbounded queue.

In any sense, in mostNThreadsThe thread is in the active state of the processing task. If an additional task is submitted when all threads are active, the additional task will wait in the queue before there is an available thread. If any thread is terminated due to a failure during the execution before it is disabled, a new thread will execute subsequent tasks (if needed) in place of it ). ExplicitlyClosePreviously, the thread in the pool will always exist.

Parameters:nThreads-Number of threads in the pool

Return Value:Newly created thread pool

Throw:IllegalArgumentException-IfNThreads <= 0

2. public static ExecutorServiceNewFixedThreadPool(Int nThreads, ThreadFactory threadFactory) creates a thread pool that can reuse a fixed number of threads and runs these threads in a shared, unbounded queue mode. When necessary, use the provided ThreadFactory to create new threads.

Parameters: nThreads-Number of threads in the pool threadFactory-Factory used to create a new thread Return Value:Newly created thread pool Throw: NullPointerException-If threadFactory is null IllegalArgumentException-If NThreads <= 0

3. public static ExecutorServiceNewSingleThreadExecutor()Create an Executor that uses a single worker thread to run this thread in an unbounded queue mode.

(Note: If this single thread is terminated because of a failure during the execution before it is disabled, a new thread will execute subsequent tasks in place of it if needed ). The tasks can be executed sequentially, and no threads are active at any given time. Equivalent to otherNewFixedThreadPool (1)Different, you can use other threads without re-configuring the execution program returned by this method.

Return Value:Newly created single-thread Executor

4. public static ExecutorServiceNewSingleThreadExecutor(ThreadFactory threadFactory) creates an Executor that uses a single worker thread, runs this thread in an unbounded queue mode, and uses the provided ThreadFactory to create a new thread as needed.

Equivalent to otherNewFixedThreadPool (1, threadFactory)Different, you can use other threads without re-configuring the execution program returned by this method.

Parameters: threadFactory-Factory used to create a new thread Return Value:Newly created single-thread Executor Throw: NullPointerException-If threadFactory is null

5. public static ExecutorServiceNewCachedThreadPool() Create a thread pool that can create new threads as needed, but reuse them when previously constructed threads are available.

For programs that execute many short-term asynchronous tasks, these thread pools can usually improve program performance. CallExecuteThe previously constructed thread will be reused (if the thread is available ). If the existing thread is not available, create a new thread and add it to the pool. Terminate and Remove unused threads from the cache for 60 seconds. Therefore, a thread pool that remains idle for a long time does not use any resources. Note: You can useThreadPoolExecutorConstructor creates a thread pool with similar properties but different details (such as timeout parameters.

Return Value:Newly created thread pool

6. public static ExecutorServiceNewCachedThreadPool(ThreadFactory threadFactory)

Create a thread pool that can create new threads as needed, but reuse the previously constructed threads when they are available, and use the provided ThreadFactory to create new threads as needed.

Parameters:threadFactory-Factory used to create a new thread

Return Value:Newly created thread pool

Throw:NullPointerException-If threadFactory is null

7. public static ScheduledExecutorServiceNewSingleThreadScheduledExecutor() Create a single-threaded execution program, which can be scheduled to run commands or regularly after a given delay.

(Note: If a single thread is terminated due to a failure during the execution before it is disabled, a new thread will execute subsequent tasks in place of it if necessary ). The tasks can be executed sequentially, and no threads are active at any given time. Equivalent to otherNewScheduledThreadPool (1)Different, you can use other threads without re-configuring the execution program returned by this method.

Return Value:Newly created scheduled execution Program

8. public static ScheduledExecutorServiceNewSingleThreadScheduledExecutor(ThreadFactory threadFactory)

Create a single-threaded execution program that can be scheduled to run commands or regularly after a given delay.

(Note: If a single thread is terminated due to a failure during the execution before it is disabled, a new thread will execute subsequent tasks in place of it if necessary ). The tasks can be executed sequentially, and no threads are active at any given time. Equivalent to otherNewScheduledThreadPool (1, threadFactory)Different, you can use other threads without re-configuring the execution program returned by this method.

Parameters:threadFactory-Factory used to create a new thread

Return Value:Newly created scheduled execution Program Throw: NullPointerException-If threadFactory is null

9. public static ScheduledExecutorServiceNewScheduledThreadPool(Int corePoolSize) to create a thread pool, which can be scheduled to run commands after a given delay or regularly run.

Parameters: corePoolSize-The number of threads stored in the pool, even if the thread is idle. Return Value:Newly created thread pool Throw: NullPointerException-If threadFactory is null

10. public static ScheduledExecutorServiceNewScheduledThreadPool(Int corePoolSize, ThreadFactory threadFactory)

Create a thread pool that can be scheduled to run commands or periodically after a given delay.

Parameters:corePoolSize-The number of threads stored in the pool, even if the thread is idle

threadFactory-The factory used by the execution program to create a new thread

Return Value:Newly created thread pool

Throw:IllegalArgumentException-IfCorePoolSize <0

NullPointerException-If threadFactory is null

11. public static ExecutorServiceUnmarshableexecutorservice(ExecutorService executor)

ReturnsExecutorServiceThe method is delegated to the object of the specified execution program, but other methods may not be accessible when forced conversion is used. This provides a way to safely "freeze" configurations and not allow you to adjust specific implementations.

Parameters:executor-Underlying implementation

Return Value:OneExecutorServiceInstance

Throw:NullPointerException-If executor is null

12. public static ScheduledExecutorServiceUnmarshablescheduledexecutorservice(ScheduledExecutorService executor)

Parameters: executor-Underlying implementation Return Value:One ScheduledExecutorServiceInstance Throw: NullPointerException-If executor is null

13. public static ThreadFactoryDefaultThreadFactory() Returns the default thread factory used to create a new thread.

This factory creates the sameThreadGroupAll new threads used by Executor. IfSecurityManager, It usesSystem.getSecurityManager()Group to call thisDefaultThreadFactoryMethod. In other cases, thread groups are used. Each new thread is created as a non-daemon and hasThread. NORM_PRIORITYAnd the maximum priority allowed in the thread group. The new thread hasPool-N-thread-MOfThread.getName()The name of the access, whereNIs the serial number of the factory,MIs the serial number of the thread created in this factory.

Return Value:Thread factory

14. public static ThreadFactoryPrivilegedThreadFactory() Return the thread factory used to create new threads. These new threads have the same permissions as the current thread.

This factory is createddefaultThreadFactory()For threads with the same settings, other settings of AccessControlContext and contextClassLoader of the new threadPrivilegedThreadFactoryThe thread of the method is the same. You canAccessController.doPrivileged(java.security.PrivilegedAction)Create a newPrivilegedThreadFactory, Set the access control context of the current thread to create a thread with the selected permissions maintained in this operation.

Note that although Tasks running in such threads have the same access control and class loaders as the current thread, they do not need to have the sameThreadLocalOrInheritableThreadLocalValue. UseThreadPoolExecutor.beforeExecute(java.lang.Thread, java.lang.Runnable)InThreadPoolExecutorBefore running any task in the subclass, you can set or reset the specific value of the local variable of the thread. In addition, if the worker thread must be initialized to have the same InheritableThreadLocal setting as some other specified threads, you can create a custom ThreadFactory in the environment where the thread waits and the service creates the request, instead of inheriting its value.

Return Value:Thread factory Throw: AccessControlException-If the current access control context does not have the permission to obtain or set the context class loader.

15. public static Callable Callable(Runnable task, T result)

ReturnCallableObject that can run a given task and return the given results. This requiresCallableMethod is useful when applied to other non-result operations.

Parameters:task-Task to run

result-Returned results