ThreadPoolExecutor

ThreadPoolExecutor线程池，java提供开发框架，管理线程的创建、销毁、优化、监控等。

有4种不同的任务队列:

1.ArrayBlockingQueue：基于数组结构的任务队列。此队列按先进先出的原则对任务进行排序。

2.LinkedBlockingQueue：基于链表结构的任务队列。此队列也是按先进先出的原则对任务进行排序。但性能比ArrayBlockingQueue高。

3.synchronousQueue：不存储元素的任务队列。每个插入操作必须等到另一个线程调用移除操作，否则插入操作一直处于阻塞状态。

4.PriorityBlockingQueue：具有优先级的任务队列。此队列中的元素必须能够比较。

拒绝策略：

RejectedExecutionHandler（饱和策略 ）：当线程池中的线程数大于maximumPoolSize时，线程池就不能在处理任何任务了，这时线程池会抛出异常。原因就是这个策略默认情况下是AbortPolicy：表示无法处理新任务时抛出异常。

1.AbortPolicy：直接抛出异常。

2.CallerRunsPolicy：只用调用者所在线程来运行任务。

3.DiscardOldestPolicy：丢弃队列里最近的一个任务，并执行当前任务

4.DiscardPolicy：不处理，丢弃掉。

自定义：

ThreadPoolExecutor.AbortPolicy()
//抛出java.util.concurrent.RejectedExecutionException异常
ThreadPoolExecutor.CallerRunsPolicy()
//重试添加当前的任务，他会自动重复调用execute()方法
ThreadPoolExecutor.DiscardOldestPolicy()
//抛弃旧的任务
ThreadPoolExecutor.DiscardPolicy()
// 抛弃当前的任务

private static class RecjectThreadHandler implements RejectedExecutionHandler { @Override public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) { } // 异常记录 private void doLog(Runnable r, ThreadPoolExecutor executor) { System.out.println(r.toString()+"excutor failed."+executor.getCompletedTaskCount()); } }

创建线程工厂：

用来创建线程。

public class CheckThreadFactory implements ThreadFactory{ private String threadGroupName; private AtomicInteger count = new AtomicInteger(0); public CheckThreadFactory(String threadGroupName) { this.threadGroupName = threadGroupName; } @Override public Thread newThread(Runnable r) { Thread thread = new Thread(r); thread.setName(threadGroupName+"--"+count.addAndGet(1)); thread.setPriority(5); thread.setDaemon(true);.// 设置为守护线程， 默认为主线程 return thread; }}

线程工具类：

/** * @author Donald * @create 2019-09-21 21:40 */public class CheckExcetPool{ // 线程池核心线程数 private static int corePoolSize = Runtime.getRuntime().availableProcessors() * 5; // 最大线程数 private static int maximumPoolSize = corePoolSize > 255 ? 255 : corePoolSize * 2; // 线程池中除了核心线程，其他线程的最大存活时间 private static int keepAliveTime = 60; // 时间单位 private static TimeUnit timeUnit = TimeUnit.SECONDS; // 线程等待队列 private static BlockingQueue queue = new LinkedBlockingQueue(); //private static BlockingQueue queue = new ArrayBlockingQueue<Runnable>(30); // 创建线程的工厂 private static CheckThreadFactory checkThreadFactory = new CheckThreadFactory("checkGroup"); // 拒绝策略 当提交任务数超过maxmumPoolSize+workQueue之和时, // * 即当提交第41个任务时(前面线程都没有执行完,此测试方法中用sleep(100)), // * 任务会交给RejectedExecutionHandler来处理 private static ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor( corePoolSize, maximumPoolSize, keepAliveTime, timeUnit, queue, checkThreadFactory ); public static void submit( Runnable runnable) { System.out.println(corePoolSize+"::"+queue.size()); threadPoolExecutor.submit(runnable); } public static <T> Future submit(Callable<T> callable) { return threadPoolExecutor.submit(callable); } public static <T> void excutor( Runnable run, T result ) { threadPoolExecutor.submit( run,result ); } public static void excutor( Runnable run) { threadPoolExecutor.execute( run); } private static class RecjectThreadHandler implements RejectedExecutionHandler { @Override public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) { } // 异常记录 private void doLog(Runnable r, ThreadPoolExecutor executor) { System.out.println(r.toString()+"excutor failed."+executor.getCompletedTaskCount()); } }}

线程服务类，实现runnable 接口：

/** * @author Donald * @create 2019-09-21 23:00 */public class ThreadService implements Runnable{ private CountDownLatch countDownLatch; private UserInterface userInterface; public ThreadService(CountDownLatch countDownLatch, UserInterface userInterface) { this.countDownLatch = countDownLatch; this.userInterface = userInterface; } @Override public void run() { try { long start = System.currentTimeMillis(); userInterface.doSomething(); System.err.println(String.format("user time :%s",System.currentTimeMillis()-start)); Thread.sleep(1000); }catch ( Exception e) { e.printStackTrace(); }finally { countDownLatch.countDown(); } }}

具体业务逻辑：

/** * @author Donald * @create 2019-09-21 22:51 */public interface UserInterface{ void doSomething();}

业务类：

/** * @author Donald * @create 2019-09-21 22:51 */public class UserService implements UserInterface{ private int number; public UserService(int number) { this.number = number; } @Override public void doSomething() { System.out.println(Thread.currentThread().getName()+"<<<<"+number); }}

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