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package com.myd.cn.ThreadPool;import java.util.concurrent.ArrayBlockingQueue;import java.util.concurrent.BlockingDeque;import java.util.concurrent.BlockingQueue;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.ThreadPoolExecutor.AbortPolicy;import java.util.concurrent.TimeUnit;public class ThreadPoolDemo { public static void test(){ //第一种方式,使用Executors.newFixedThreadPool(10) //ExecutorService executorService = Executors.newFixedThreadPool(10); //第二种,使用new ThreadPoolExecutor(方法签名),指定具体参数,设置拒绝策略 BlockingQueueworkQueue = new ArrayBlockingQueue(100); AbortPolicy rejectPolicy = new AbortPolicy(); //keepaliveTime设置为0,意味线程空闲多久都不退出 ThreadPoolExecutor pool = new ThreadPoolExecutor(3, 3, 0, TimeUnit.SECONDS, workQueue,rejectPolicy); //设置拒绝策略 //pool.setRejectedExecutionHandler(rejectPolicy); //使用lambda方式向线程池提交任务 pool.execute(()->{ System.out.println("lambda style is executed"); }); } public static void main(String[] args) { test(); }}
1.是有界设计,如果容量满无法继续添加,纸质有元素被移除才能继续添加新的就绪任务。2.数组性阻塞队列,初始化一定容量的数组3.使用一个重入锁(默认非公平),入队和出队共用一个锁,互斥。4..数组型,使用时开辟连续内存,若初始容量过大易造成资源浪费,过小易添加失败。
1.有边界设计,默认构造方法容量是Integer.MAX_VALUE2.使用两个重入锁分布控制元素的入队和出队,用Condition(条件变量,可以在线程间唤醒和等待绑定多余一个的条件)3.链表实现,申请空间是非连续性
1.无边界设计2.添加(put)不阻塞,移除(remove)时阻塞3.元素都有一个过期时间4.取元素时只有过期的才会被取出
1.内部容量为02.每次删除都要等待插入操作3.每次插入都要等于删除操作4.一个元素,一旦有了插入线程和移除线程,那么很快由插入线程移交移除线程,该容器相当于通道本身不存储元素5.多任务队列中,是最快的处理方式
1.无边界设计,容量依靠自有系统资源影响(资源多则多分配,少则少分配)2.添加元素,如果超过1,则进入优先级排序
1.定时执行异步任务周期性执行异步任务,例子如下2.当前时间开始,每个5s打印 "is Running" package com.myd.cn.ThreadLocal; import java.util.concurrent.ScheduledThreadPoolExecutor; import java.util.concurrent.TimeUnit; public class ScheduledExecutorPoolDemo { public static void testScheduledThreadPoolExecutor() throws Exception { ScheduledThreadPoolExecutor scheduledExecutorPool = new ScheduledThreadPoolExecutor(10); scheduledExecutorPool.scheduleAtFixedRate(()->{ System.out.println("is Running"); }, 0, 5, TimeUnit.SECONDS); } public static void main(String[] args) throws Exception { testScheduledThreadPoolExecutor(); } }3.输出结果 is Running is Running is Running
1.线程从和异常的监控和告警,及时了解任务运行状况2.周期性执行任务,需要注意任务的执行时间,避免业务影响3.注意异常处理,抛出异常后,任务将终止周期执行
public void execute(Runnable command) { schedule(command, 0, NANOSECONDS);}
public ScheduledFuture schedule(Runnable command, long delay, TimeUnit unit) { if (command == null || unit == null) throw new NullPointerException(); RunnableScheduledFuture t = decorateTask(command, new ScheduledFutureTask(command, null, triggerTime(delay, unit))); delayedExecute(t); return t;} 2.修改和替换用来执行一个runnable的任务protected RunnableScheduledFuture decorateTask( Runnable runnable, RunnableScheduledFuture task) { return task; }3.设置触发事件(距现在多久执行) private long triggerTime(long delay, TimeUnit unit) { return triggerTime(unit.toNanos((delay < 0) ? 0 : delay));}
public void run() { boolean periodic = isPeriodic(); if (!canRunInCurrentRunState(periodic)) cancel(false); else if (!periodic) ScheduledFutureTask.super.run(); else if (ScheduledFutureTask.super.runAndReset()) { setNextRunTime(); reExecutePeriodic(outerTask); } }
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