Java线程池

ThreadFactory threadFactory= Executors.defaultThreadFactory();

RejectedExecutionHandler handler =new ThreadPoolExecutor.CallerRunsPolicy();

int corePoolSize= Runtime.getRuntime().availableProcessors();

------------ThreadPoolExecutor---------

Executor executor1 =new ThreadPoolExecutor(5,10,1, TimeUnit.SECONDS,queue);

ExecutorService executor2 =new ThreadPoolExecutor(5,10,1, TimeUnit.SECONDS,queue,threadFactory);

ThreadPoolExecutor executor3 =new ThreadPoolExecutor(5,10,1, TimeUnit.SECONDS,queue,threadFactory,handler);

----------- ScheduledThreadPoolExecutor---------

Executor scheduledExecutorService1 =new ScheduledThreadPoolExecutor(5);

ExecutorService scheduledExecutorService2 =new ScheduledThreadPoolExecutor(5,threadFactory);

ScheduledExecutorService scheduledExecutorService3 =new ScheduledThreadPoolExecutor(5,handler);

ScheduledThreadPoolExecutor scheduledExecutorService4 =new ScheduledThreadPoolExecutor(5,threadFactory,handler);

------------Executors创建4种线程池------------

1.创建一个可缓存的线程池。如果线程池的大小超过了处理任务所需要的线程，那么就会回收部分空闲（60秒不执行任务）的线程，当任务数增加时，此线程池又可以智能的添加新线程来处理任务。此线程池不会对线程池大小做限制，线程池大小完全依赖于操作系统（或者说JVM）能够创建的最大线程大小。

ExecutorService executorService = Executors.newCachedThreadPool();

源码:return new ThreadPoolExecutor(0, Integer.MAX_VALUE,60L, TimeUnit.SECONDS,new SynchronousQueue());

2.创建一个单线程的线程池。这个线程池只有一个线程在工作，也就是相当于单线程串行执行所有任务。如果这个唯一的线程因为异常结束，那么会有一个新的线程来替代它。此线程池保证所有任务的执行顺序按照任务的提交顺序执行。

ExecutorService executorService1 = Executors.newSingleThreadExecutor();

源码:return new FinalizableDelegatedExecutorService(new ThreadPoolExecutor(1,1,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue()));

ExecutorService executorService2 = Executors.newSingleThreadExecutor(threadFactory);

源码:return new FinalizableDelegatedExecutorService(new ThreadPoolExecutor(1,1,0L, TimeUnit.MILLISECONDS,newLinkedBlockingQueue(),threadFactory));

3.创建固定大小的线程池。每次提交一个任务就创建一个线程，直到线程达到线程池的最大大小。线程池的大小一旦达到最大值就会保持不变，如果某个线程因为执行异常而结束，那么线程池会补充一个新线程。

ExecutorService executorService3 = Executors.newFixedThreadPool(nThreads);

源码:return new ThreadPoolExecutor(nThreads, nThreads,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue());

ExecutorService executorService4 = Executors.newFixedThreadPool(nThreads,threadFactory);

源码:return new ThreadPoolExecutor(nThreads, nThreads,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue(),threadFactory);

4.创建一个大小无限的线程池。此线程池支持定时以及周期性执行任务的需求。

ExecutorService executorService5 = Executors.newScheduledThreadPool(corePoolSize);

源码:return new ScheduledThreadPoolExecutor(corePoolSize);

ExecutorService executorService6 = Executors.newScheduledThreadPool(corePoolSize,threadFactory);

源码:return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);

初心：学到手里的知识才是自己的，如有不妥，欢迎指正。