| 一、使用Executors创建线程池
之前创建线程的时候都是用的Executors的newFixedThreadPool(),newSingleThreadExecutor(),newCachedThreadPool()这三个方法。
1. newFixedThreadPool()
创建线程数固定大小的线程池。
2.newSingleThreadPool()
创建线程数为1的线程池，
3.newCachedThreadPool()
创建可缓冲的线程池。没有大小限制
二、使用ThreadPoolExecutor创建线程池
ThreadPoolExecutor的构造函数 - public ThreadPoolExecutor(int corePoolSize,
- int maximumPoolSize,
- long keepAliveTime,
- TimeUnit unit,
- BlockingQueue<Runnable> workQueue,
- ThreadFactory threadFactory,
- RejectedExecutionHandler handler) {
- 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;
- }
1、corePoolSize核心线程数大小，当线程数
2、maximumPoolSize 最大线程数， 当线程数 >= corePoolSize的时候，会把runnable放入workQueue中
3、keepAliveTime 保持存活时间，当线程数大于corePoolSize的空闲线程能保持的最大时间。
4、unit 时间单位
5、workQueue 保存任务的阻塞队列
6、threadFactory 创建线程的工厂
7、handler 拒绝策略
任务执行顺序：
1、当线程数小于corePoolSize时，创建线程执行任务。
2、当线程数大于等于corePoolSize并且workQueue没有满时，放入workQueue中
3、线程数大于等于corePoolSize并且当workQueue满时，新任务新建线程运行，线程总数要小于maximumPoolSize
4、当线程总数等于maximumPoolSize并且workQueue满了的时候执行handler的rejectedExecution。也就是拒绝策略。
ThreadPoolExecutor默认有四个拒绝策略：
1、ThreadPoolExecutor.AbortPolicy() 直接抛出异常RejectedExecutionException
2、ThreadPoolExecutor.CallerRunsPolicy() 直接调用run方法并且阻塞执行
3、ThreadPoolExecutor.DiscardPolicy() 直接丢弃后来的任务
4、ThreadPoolExecutor.DiscardOldestPolicy() 丢弃在队列中队首的任务
当然可以自己继承RejectedExecutionHandler来写拒绝策略. - int corePoolSize = 1;
- int maximumPoolSize = 2;
- int keepAliveTime = 10;
- // BlockingQueue<Runnable> workQueue = new LinkedBlockingQueue<Runnable>();
- BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<Runnable>(5);
- ThreadFactory threadFactory = Executors.defaultThreadFactory();
- //线程池和队列满了之后的处理方式
- //1.跑出异常
- RejectedExecutionHandler handler = new ThreadPoolExecutor.AbortPolicy();
- RejectedExecutionHandler handler2 = new ThreadPoolExecutor.CallerRunsPolicy();
- RejectedExecutionHandler handler3 = new ThreadPoolExecutor.DiscardPolicy();
- RejectedExecutionHandler handler4 = new ThreadPoolExecutor.DiscardOldestPolicy();
-
- ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, TimeUnit.SECONDS, workQueue, threadFactory, handler2);
-
-
- for (int j = 1; j < 15; j++) {
- threadPoolExecutor.execute(new Runnable() {
-
- public void run() {
-
- try {
- System.out.println(Thread.currentThread().getName());
- TimeUnit.SECONDS.sleep(1);
- } catch (InterruptedException e) {
- e.printStackTrace();
- }
-
-
- }
- });
- }
-
- System.out.println(threadPoolExecutor);
-
- }
来自：http://my.oschina.net/u/2250599/blog/498787 | 
