台州行app官网下载,sem优化方法,最新网站推广哪家好,wordpress导入导出一、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。当然Executors也是用不同的参数去new ThreadPoolExecutor1. newFixedThreadPool()创建线程数固定大小的线程池。 由于使用…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。当然Executors也是用不同的参数去new ThreadPoolExecutor1. newFixedThreadPool()创建线程数固定大小的线程池。 由于使用了LinkedBlockingQueue所以maximumPoolSize 没用当corePoolSize满了之后就加入到LinkedBlockingQueue队列中。每当某个线程执行完成之后就从LinkedBlockingQueue队列中取一个。所以这个是创建固定大小的线程池。public static ExecutorService newFixedThreadPool(int nThreads) {return new ThreadPoolExecutor(nThreads, nThreads,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue());}public ThreadPoolExecutor(int corePoolSize,int maximumPoolSize,long keepAliveTime,TimeUnit unit,BlockingQueue workQueue) {this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,Executors.defaultThreadFactory(), defaultHandler);}2.newSingleThreadPool()创建线程数为1的线程池由于使用了LinkedBlockingQueue所以maximumPoolSize 没用corePoolSize为1表示线程数大小为1,满了就放入队列中执行完了就从队列取一个。public static ExecutorService newSingleThreadExecutor() {return new FinalizableDelegatedExecutorService(new ThreadPoolExecutor(1, 1,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue()));}3.newCachedThreadPool()创建可缓冲的线程池。没有大小限制。由于corePoolSize为0所以任务会放入SynchronousQueue队列中SynchronousQueue只能存放大小为1所以会立刻新起线程由于maxumumPoolSize为Integer.MAX_VALUE所以可以认为大小为2147483647。受内存大小限制。public static ExecutorService newCachedThreadPool() {return new ThreadPoolExecutor(0, Integer.MAX_VALUE,60L, TimeUnit.SECONDS,new SynchronousQueue());}public ThreadPoolExecutor(int corePoolSize,int maximumPoolSize,long keepAliveTime,TimeUnit unit,BlockingQueue workQueue) {this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,Executors.defaultThreadFactory(), defaultHandler);}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 workQueue,ThreadFactory threadFactory,RejectedExecutionHandler handler) {if (corePoolSize maximumPoolSize 0 ||maximumPoolSize keepAliveTime 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;}参数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maximumPoolSize4、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RejectedExecutionException2、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 workQueue new LinkedBlockingQueue();BlockingQueue workQueue new ArrayBlockingQueue(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 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);}
