下面若是有贴出源码,对应的源码是JDK8java
主要的源码类源码分析
java.util.concurrent.ThreadPoolExecutor、
java.util.concurrent.ThreadPoolExecutor.Worker
java.util.concurrent.AbstractExecutorServicethis
public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) 复制代码
内部有重要的成员变量ctl,类型是AtomicInteger,低29位表示线程池中线程数,经过高3位表示线程池的运行状态spa
COUNT_BITS的值是29线程
execute --> addWorker --> Thread.start --> (Thread.run) --> runTask --> getTaskcode
3.1execute(Runnable command)orm
大体分三个步骤cdn
3.2 addWorker(Runnable firstTask, boolean core)对象
3.3 runWorker(Worker w)blog
经过循环调用getTask()获取要执行的任务task
beforeExecute
task.run()
afterExecute
3.4 getTask()
源码以下:
private Runnable getTask() {
Boolean timedOut = false;
// 是否最后的 poll() 超时了?
for (;;) {
int c = ctl.get();
int rs = runStateOf(c);
// Check if queue empty only if necessary.
if (rs >= SHUTDOWN && (rs >= STOP || workQueue.isEmpty())) {
decrementWorkerCount();
return null;
}
int wc = workerCountOf(c);
Boolean timed = allowCoreThreadTimeOut || wc > corePoolSize;
// worker是否须要被淘汰
if ((wc > maximumPoolSize || (timed && timedOut))
&& (wc > 1 || workQueue.isEmpty())) {
// 这里会让线程的数量记录减,后面的return null,会致使runWorker没有获取到数据而让run()方法走到尽头,最终当前线程结束
if (compareAndDecrementWorkerCount(c))
return null;
continue;
}
try {
// 若是须要回收一部分线程,那么超时时间keepAliveTime后拿不到就数据就继续循环调用,就能够在下一次循环的时候进行线程结束回收了;不然一直阻塞下去
Runnable r = timed ?
workQueue.poll(keepAliveTime, TimeUnit.NANOSECONDS) :
workQueue.take();
if (r != null)
return r;
timedOut = true;
}
catch (InterruptedException retry) {
timedOut = false;
}
}
}
复制代码
源码以下:
public <T> Future<T> submit(Callable<T> task) {
if (task == null) throw new NullPointerException();
RunnableFuture<T> ftask = newTaskFor(task);
execute(ftask);
return ftask;
}
public Future<?> submit(Runnable task) {
if (task == null) throw new NullPointerException();
RunnableFuture<Void> ftask = newTaskFor(task, null);
execute(ftask);
return ftask;
}
复制代码
代码比较简单,把任务封装成一个既实现Runnable, 也实现Future<v style="margin: 0px; padding: 0px;">
的接口,这个时候就能够调用execute()
进行实现了</v>