ThreadPoolExecutor
1、线程池5个运行状态
RUNNING: Accept new tasks and process queued tasks
SHUTDOWN: Don't accept new tasks, but process queued tasks
STOP: Don't accept new tasks, don't process queued and interrupt in-progress tasks
TIDYING: All tasks have terminated, workerCount is zero, the thread transitioning to state TIDYING will run the terminated() hook method
TERMINATED: terminated() has completed
RUNNING -> SHUTDOWN
On invocation of shutdown(), perhaps implicitly in finalize()
(RUNNING or SHUTDOWN) -> STOP
On invocation of shutdownNow()
SHUTDOWN -> TIDYING
When both queue and pool are empty
STOP -> TIDYING
When pool is empty
TIDYING -> TERMINATED
When the terminated() hook method has completed
2、几个重要属性
corePoolSize、maximumPoolSize、threadFactory、keepAliveTime、workQueue.
When a new task is submitted in method {@link #execute(Runnable)},
and fewer than corePoolSize threads are running, a new thread is
created to handle the request, even if other worker threads are
idle. If there are more than corePoolSize but less than
maximumPoolSize threads running, a new thread will be created only
if the queue is full. By setting corePoolSize and maximumPoolSize
the same, you create a fixed-size thread pool. By setting
maximumPoolSize to an essentially unbounded value such as {@code
Integer.MAX_VALUE}, you allow the pool to accommodate an arbitrary
number of concurrent tasks. Most typically, core and maximum pool
sizes are set only upon construction, but they may also be changed
dynamically using {@link #setCorePoolSize} and {@link
#setMaximumPoolSize}. </dd>
