轉(zhuǎn) https://blog.csdn.net/weixin_43893397/article/details/104361154

【1】代碼示例?

/*** 線程池測(cè)試-自定義線程池創(chuàng)建方式* @since 2021/03/23 */ public class ThreadPoolMain2 {public static void main(String[] args) throws Exception {newMethod();}public static void newMethod() throws InterruptedException {/*** 開啟一個(gè)線程池 默認(rèn)線程是10個(gè)* 使用默認(rèn)線程工廠* 拒絕策略為CallerRunsPolicy策略，讓后面的線程先等待 */ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(10, 10, 1000L, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(10),Executors.defaultThreadFactory(),new ThreadPoolExecutor.CallerRunsPolicy());//書寫一個(gè)循環(huán) 模擬100個(gè)用戶同時(shí)訪問(wèn)for (int request = 0; request< 100;request ++){final int temp = request; //開啟一個(gè)線程threadPoolExecutor.execute(() ->{System.out.println("任務(wù)" + temp +"開始執(zhí)行...");/*** 睡10秒 */try {Thread.sleep(1000L * 3);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("任務(wù)" + temp +"執(zhí)行結(jié)束...");});}} }

【2】 ThreadPoolExecutor 構(gòu)造器解析

/*** Creates a new {@code ThreadPoolExecutor} with the given initial* parameters.** @param corePoolSize the number of threads to keep in the pool, even* if they are idle, unless {@code allowCoreThreadTimeOut} is set* @param maximumPoolSize the maximum number of threads to allow in the* pool* @param keepAliveTime when the number of threads is greater than* the core, this is the maximum time that excess idle threads* will wait for new tasks before terminating.* @param unit the time unit for the {@code keepAliveTime} argument* @param workQueue the queue to use for holding tasks before they are* executed. This queue will hold only the {@code Runnable}* tasks submitted by the {@code execute} method.* @param threadFactory the factory to use when the executor* creates a new thread* @param handler the handler to use when execution is blocked* because the thread bounds and queue capacities are reached* @throws IllegalArgumentException if one of the following holds:<br>* {@code corePoolSize < 0}<br>* {@code keepAliveTime < 0}<br>* {@code maximumPoolSize <= 0}<br>* {@code maximumPoolSize < corePoolSize}* @throws NullPointerException if {@code workQueue}* or {@code threadFactory} or {@code handler} is null*/public ThreadPoolExecutor(int corePoolSize,int maximumPoolSize,long keepAliveTime,TimeUnit unit,BlockingQueue<Runnable> workQueue,ThreadFactory threadFactory,RejectedExecutionHandler handler) {

【3】參數(shù)解析

序號(hào)	參數(shù)名	描述	中文
1	corePoolSize	the number of threads to keep in the pool, even if they are idle, unless {@code allowCoreThreadTimeOut} is set.	除非設(shè)置了{(lán)@code allowCoreThreadTimeOut}，否則即使它們處于空閑狀態(tài)也要保留在池中的線程數(shù)。
2	maximumPoolSize	?the maximum number of threads to allow in the pool	池中允許的最大線程數(shù)
3	keepAliveTime	when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.	當(dāng)線程數(shù)大于內(nèi)核數(shù)時(shí)，這是多余的空閑線程將在終止之前等待新任務(wù)的最長(zhǎng)時(shí)間。
4	unit	the time unit for the {@code keepAliveTime} argument	{@code keepAliveTime}參數(shù)的時(shí)間單位
5	workQueue	?the queue to use for holding tasks before they are executed. This queue will hold only the Runnable tasks submitted by the execute method.	在執(zhí)行任務(wù)之前用于保留任務(wù)的隊(duì)列。 此隊(duì)列將僅保存execute方法提交的Runnable任務(wù)。
6	threadFactory	the factory to use when the executorcreates a new thread.	執(zhí)行程序創(chuàng)建新線程時(shí)要使用的工廠。
7	handler	?the handler to use when execution is blockedbecause the thread bounds and queue capacities are reached.	當(dāng)執(zhí)行被阻塞時(shí)使用的處理程序，因?yàn)檫_(dá)到了線程界限和隊(duì)列容量。

【4】拋棄策略

// 當(dāng)任務(wù)無(wú)法添加到阻塞隊(duì)列時(shí)的處理策略-直接拋出異常RejectedExecutionHandler rejectHandler1 = new ThreadPoolExecutor.AbortPolicy(); // -會(huì)調(diào)用當(dāng)前線程池的所在的線程去執(zhí)行被拒絕的任務(wù)。RejectedExecutionHandler rejectHandler2 = new ThreadPoolExecutor.CallerRunsPolicy(); // 會(huì)拋棄任務(wù)隊(duì)列中最舊的任務(wù)也就是最先加入隊(duì)列的，再把這個(gè)新任務(wù)添加進(jìn)去。RejectedExecutionHandler rejectHandler3 = new ThreadPoolExecutor.DiscardOldestPolicy();// 會(huì)讓被線程池拒絕的任務(wù)直接拋棄，不會(huì)拋異常也不會(huì)執(zhí)行。RejectedExecutionHandler rejectHandler4 = new ThreadPoolExecutor.DiscardPolicy(); RejectedExecutionHandler rejectHandler = rejectHandler4; ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(10, 10, 1000L, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(10),Executors.defaultThreadFactory(), rejectHandler);

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