package com.mandi.fendan.util;
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import javax.validation.constraints.NotNull;
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import java.util.concurrent.LinkedBlockingQueue;
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import java.util.concurrent.ThreadFactory;
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import java.util.concurrent.ThreadPoolExecutor;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.atomic.AtomicInteger;
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/**
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* 线程池的工具类
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* 用于进行线程的管理，防止重复创建、杀死线程。
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*
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* 多线程运行期间，如果系统不断的创建、杀死新线程，
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* 会产生过度消耗系统资源，以及过度切换线程的问题，甚至可能导致系统资源的崩溃。
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* 因此需要线程池，对线程进行管理。
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*/
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public class ThreadPoolUtil {
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private String TAG = getClass().getName();
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private static volatile ThreadPoolUtil mInstance;
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//核心线程池的数量，同时能够执行的线程数量
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private int corePoolSize;
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//最大线程池数量，表示当缓冲队列满的时候能继续容纳的等待任务的数量
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private int maxPoolSize;
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//存活时间
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private long keepAliveTime = 1;
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private TimeUnit unit = TimeUnit.HOURS;
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private ThreadPoolExecutor executor;
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private ThreadPoolUtil() {
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//给corePoolSize赋值：当前设备可用处理器核心数*2 + 1,能够让cpu的效率得到最大程度执行（有研究论证的）
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corePoolSize = Runtime.getRuntime().availableProcessors() * 2 + 1;
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maxPoolSize = corePoolSize;
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executor = new ThreadPoolExecutor(
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//当某个核心任务执行完毕，会依次从缓冲队列中取出等待任务
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corePoolSize,
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// 然后new LinkedBlockingQueue(),然后maximumPoolSize,但是它的数量是包含了corePoolSize的
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maxPoolSize,
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//表示的是maximumPoolSize当中等待任务的存活时间
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keepAliveTime,
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unit,
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//缓冲队列，用于存放等待任务，Linked的先进先出
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new LinkedBlockingQueue(),
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new DefaultThreadFactory(Thread.NORM_PRIORITY, "thread-pool-"),
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new ThreadPoolExecutor.AbortPolicy()
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);
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}
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public static ThreadPoolUtil getInstance() {
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if (mInstance == null) {
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synchronized (ThreadPoolUtil.class) {
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if (mInstance == null) {
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mInstance = new ThreadPoolUtil();
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}
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}
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}
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return mInstance;
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}
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/**
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* 执行任务
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*
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* @param runnable
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*/
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public void execute(Runnable runnable) {
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if (executor == null) {
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executor = new ThreadPoolExecutor(
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corePoolSize,
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maxPoolSize,
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keepAliveTime,
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TimeUnit.SECONDS,
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new LinkedBlockingQueue(),
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new DefaultThreadFactory(Thread.NORM_PRIORITY, "thread-pool-"),
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new ThreadPoolExecutor.AbortPolicy());
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}
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if (runnable != null) {
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executor.execute(runnable);
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}
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}
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/**
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* 移除任务
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*
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* @param runnable
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*/
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public void remove(Runnable runnable) {
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if (runnable != null) {
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executor.remove(runnable);
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}
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}
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private static class DefaultThreadFactory implements ThreadFactory {
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//线程池的计数
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private static final AtomicInteger poolNumber = new AtomicInteger(1);
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//线程的计数
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private final AtomicInteger threadNumber = new AtomicInteger(1);
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private final ThreadGroup group;
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private final String namePrefix;
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private final int threadPriority;
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DefaultThreadFactory(int threadPriority, String threadNamePrefix) {
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this.threadPriority = threadPriority;
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this.group = Thread.currentThread().getThreadGroup();
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this.namePrefix = threadNamePrefix + poolNumber.getAndIncrement() + "-thread-";
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}
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@Override
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public Thread newThread(@NotNull Runnable r) {
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Thread thread = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0);
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// 返回True该线程就是守护线程
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// 守护线程应该永远不去访问固有资源，如：数据库、文件等。因为它会在任何时候甚至在一个操作的中间发生中断。
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if (thread.isDaemon()) {
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thread.setDaemon(false);
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}
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thread.setPriority(threadPriority);
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return thread;
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}
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}
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}
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