上一篇：Android多线程之ThreadPoolExecutor与四大线程池
ThreadPoolExecutor构造函数
public ThreadPoolExecutor(int corePoolSize, //核心线程数
int maximumPoolSize, //最大线程数
long keepAliveTime, //线程存活时间
TimeUnit unit, //时间类型
BlockingQueue<Runnable> workQueue, //阻塞队列
ThreadFactory threadFactory, //线程工厂
RejectedExecutionHandler handler) { //拒绝策略
if (corePoolSize < 0 ||
maximumPoolSize <= 0 ||
maximumPoolSize < corePoolSize ||
keepAliveTime < 0)
throw new IllegalArgumentException();
if (workQueue == null || threadFactory == null || handler == null)
throw new NullPointerException();
this.corePoolSize = corePoolSize;
this.maximumPoolSize = maximumPoolSize;
this.workQueue = workQueue;
this.keepAliveTime = unit.toNanos(keepAliveTime);
this.threadFactory = threadFactory;
this.handler = handler;
}
创建线程池实例
ThreadPoolExecutor executor = new ThreadPoolExecutor(
5,
10,
1000,
TimeUnit.MILLISECONDS,
new LinkedBlockingDeque<Runnable>(9),
new ThreadFactory() {
@Override
public Thread newThread (Runnable r) {
return new Thread(r);
}
});
执行execute
executor.execute(new Runnable() {
@Override
public void run () {
//执行任务
Log.d(TAG, "executor() called i = " );
}
});
分析ThreadPoolExecutor的execute方法
public void execute(Runnable command) {
if (command == null)
throw new NullPointerException();
/*
* 1. 如果当前运行的线程数<核心线程数,创建一个新的线程执行任务,
* 调用addWorker方法原子性地检查运行状态和线程数,通过返回false防止不需要的时候添加线程。
*
* 2. 如果一个任务能够成功的入队,仍然需要双重检查,
* 因为我们添加了一个线程(有可能这个线程在上次检查后就已经死亡了)
* 或者进入此方法的时候调用了shutdown,所以需要重新检查线程池的状态,如果必要的话,
* 当停止的时候要回滚入队操作,或者当线程池为空的话创建一个新的线程
*
* 3. 如果不能入队,尝试着开启一个新的线程,如果开启失败,说明线程池已经是shutdown状态或饱和了,
* 所以拒绝执行该任务
*/
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);
}
参考文章
