????Java?????????????????????
????· ????????ThreadPoolExecutor
????· ???Executors.newCachedThreadPool()
????· ???Executors.newFixedThreadPool(int)
????· ???Executors.newSingleThreadExecutor()
???????????2??3??4????????????????????????ThreadPoolExecutor????????????????????????ThreadPoolExecutor??????????????????
???????????
????ThreadPoolExecutor??????????????￡??????????????????????????
????public ThreadPoolExecutor(int corePoolSize??
????int maximumPoolSize??
????long keepAliveTime??
????TimeUnit unit??
????BlockingQueue<Runnable> workQueue??
????ThreadFactory threadFactory??
????RejectedExecutionHandler handler)
????corePoolSize??maximumPoolSize
?????????????????????????????????????????????????1???????????С??corePoolSize??2???????????????corePoolSize??С??maximumPoolSize?????????????????
???????????????maximumPoolSize??corePoolSize?????????????????????????????????????????????????
????keepAliveTime??timeUnit
??????????????г???corePoolSize????????????????????????keepAliveTime?????λ??timeUnit????????????????
???????????????????????corePoolSize????????????????????allowCoreThreadTimeOut(boolean)???????corePoolSize?е?????????Ч??
????workQueue
????workQueue????????????????У??κ??????BlockingQueue???????????????С?
??????????к????????????????????????????????????????????
????????????????corePoolSize??????????????????????????????????????????????У????????
?????????????????corePoolSize??????????workQueue.offer(command)??????????????????????????е??????С?
?????????????????????????С??maximumPoolSize??????????????????????????????
????workQueue.offer????????????????????????????????????????????????workQueue????????磬?????? LinkedBlockingQueue ????????????????????????workQueue.offer???????????? SynchronousQueue ???????????????????????????????????workQueue.offer???????????????????????????
????ThreadFactory
??????????????????????????threadFactory.newThread(Runnable r)????????????
????ThreadFactory???????????newThread?????????????????????
????class SimpleThreadFactory implements ThreadFactory {
????public Thread newThread(Runnable r) {
????return new Thread(r);
????}
????}
???????????????? Executors.defaultThreadFactory() ?????????????ThreadFactory??????????????????
????RejectedExecutionHandler
????????????????????????????????????????????????
??????????????
???????????maximumPoolSize???????????????
???????濴???????????????????
????ThreadPoolExecutor.AbortPolicy ????????????RejectedExecutionException?????????????????????
????ThreadPoolExecutor.CallerRunsPolicy ???????????????????????
????ThreadPoolExecutor.DiscardPolicy ????????????????
????ThreadPoolExecutor.DiscardOldestPolicy ???????????δ??е???????????????
??????????
????ThreadPoolExecutor?????????????????????????????????С?
??????????????????????????ThreadPoolExecutor.execute??????????????????ThreadPoolExecutor????е??????????????????????????????????????????????????????ThreadPoolExecutor??????????????????????磬???????????????????????????????????????????????????????
?????????????????????????????????????????
????· ThreadPoolExecutor??
????· ??????
????· ??????????????
??????????
????ThreadPoolExecutor??5???????????????
????Running?????????????????????????
????Shutdown?????????????????????????????
????Stop??????????????????????????????????????????е?????
????Tidying??????????????????????????????????????????terminated()???????
????Terminated??terminated()??????????
????ThreadPoolExecutor?????????32bit?????? ctl ???????????????????????????????????
????private final AtomicInteger ctl = new AtomicInteger(ctlOf(RUNNING?? 0));
????private static final int COUNT_BITS = Integer.SIZE - 3;
????//??????
????private static final int RUNNING    = -1 << COUNT_BITS;
????private static final int SHUTDOWN   =  0 << COUNT_BITS;
????private static final int STOP       =  1 << COUNT_BITS;
????private static final int TIDYING    =  2 << COUNT_BITS;
????private static final int TERMINATED =  3 << COUNT_BITS;
????//rs??runState?????????????wc??workerCount???????????????????????????????????????32bit??????
????private static int ctlOf(int rs?? int wc) { return rs | wc; }
????ctl?32bit????????????????????????λ3??bit??????????λ29??bit??????????λ3??bit???????????￡?
????111??Running
????000??Shutdown
????001??Stop
????010??Tidying
????011??Terminated
?????????ctl?????????????Running????????????????????????????????????????????????????????Running < Shutdown < Stop < Tidying < Terminated??
??????????
??????????????￡?
public void execute(Runnable command) {
if (command == null)
throw new NullPointerException();
int c = ctl.get();
if (workerCountOf(c) < corePoolSize) {
if (addWorker(command?? true))
return;
c = ctl.get();
}
if (isRunning(c) && workQueue.offer(command)) {
int recheck = ctl.get();
if (! isRunning(recheck) && remove(command))
reject(command);
else if (workerCountOf(recheck) == 0)
addWorker(null?? false);
}
else if (!addWorker(command?? false))
reject(command);
}
??????????????????????????
???????????ctl.get()?????????????????workerCountOf(c)??????????е????????????
???????????????С??corePoolSize?????????addWorker?????????????????????????????????????????????????????в???3???????????????????1?????????????2?????????????????????????????????????????????????????corePoolSize??
?????????????????????????????workQueue.offer????????????С????????????????????е????????????????????????????????ж???????????????Running???????????????????о??????????????????????0?????????????????????????С??????????в???4??