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ThreadPoolExecutor 提供了强大的灵活性和自定义参数的能力，可以根据实际需求来灵活配置线程池的行为。位置
java.util.concurrent 包下
构造函数
public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue)public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory)public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler)\public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler)核心参数
corePoolSize：线程池的基本大小，即使没有任务执行时也保持存活的线程数。
maximumPoolSize：线程池所能容纳的最大线程数（包括核心线程）。
keepAliveTime：非核心线程空闲等待新任务的最长时间，在这个时间内如果没有新任务提交，那么非核心线程将会被终止。
unit：与keepAliveTime搭配使用的单位，如TimeUnit.SECONDS或TimeUnit.MILLISECONDS等。
workQueue：任务队列，用于保存待处理的任务，可以是无界队列（例如LinkedBlockingQueue）或有界队列（例如ArrayBlockingQueue）。
threadFactory：创建新线程的工厂，默认使用Executors.defaultThreadFactory()，也可以自定义来设置线程名称、优先级等属性。
handler：拒绝策略，当线程池和工作队列都已满，无法接收新的任务时，会调用此策略进行处理。AbortPolicy（直接抛出异常）；CallerRunsPolicy（由调用者线程自己执行任务）；DiscardPolicy（直接丢弃新任务）；DiscardOldestPolicy（丢弃队列中最旧的任务并尝试提交当前任务）。线程池工作流程
当一个任务提交到ThreadPoolExecutor时：
如果当前运行的线程数量小于corePoolSize，则创建一个新的线程来执行任务。
若当前线程数等于corePoolSize但小于maximumPoolSize，且工作队列已满，则创建新的线程来执行任务。
如果线程数已经达到maximumPoolSize并且工作队列也满了，则根据RejectedExecutionHandler策略处理该任务。线程池状态
线程池具有五种状态：RUNNING、SHUTDOWN、STOP、TIDYING 和 TERMINATED。
状态转换通常发生在调用诸如shutdown(), shutdownNow(), 或者所有任务完成后重要方法
shutdown():线程池不再接受新的任务，但会继续处理已经提交的任务。
shutdownNow():尝试停止所有正在执行的任务，并返回尚未开始执行的任务列表。
execute(Runnable command)：提交一个Runnable任务给线程池执行。
submit(Callable<T> task)：提交一个Callable任务，能够返回结果。
awaitTermination(long timeout, TimeUnit unit)：阻塞当前线程，直到线程池关闭或者超时发生。
isTerminated()：检查线程示例
示例1：
package org.springblade.test;import lombok.extern.slf4j.Slf4j;import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;@Slf4j
public class Test {@org.junit.jupiter.api.Testpublic void ThreadPoolExecutorExample() {// 自定义线程工厂ThreadFactory namedThreadFactory = new NamedThreadFactory();// 创建有界任务队列BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(10);// 定义拒绝策略RejectedExecutionHandler handler = new ThreadPoolExecutor.CallerRunsPolicy();// 创建线程池ThreadPoolExecutor executor = new ThreadPoolExecutor(2, // 核心线程数4, // 最大线程数60L, // 空闲线程存活时间（单位：秒）TimeUnit.SECONDS, // 时间单位workQueue, // 工作队列namedThreadFactory, // 线程工厂handler // 拒绝策略);// 提交任务到线程池for (int i = 0; i < 20; i++) {final int taskId = i;Runnable worker = new Runnable() {@Overridepublic void run() {System.out.println("Task " + taskId + " is running by " + Thread.currentThread().getName());try {Thread.sleep(500); // 模拟耗时操作} catch (InterruptedException e) {e.printStackTrace();}System.out.println("Task " + taskId + " finished");}};executor.execute(worker);}// 关闭线程池executor.shutdown();while (!executor.isTerminated()) {// 等待所有任务执行完毕}System.out.println("所有任务已完成，线程池已关闭");}
}/*** 定义线程创建逻辑，设置线程名称前缀等*/
class NamedThreadFactory implements ThreadFactory {private static final AtomicInteger poolNumber = new AtomicInteger(1);private final ThreadGroup group;private final AtomicInteger threadNumber = new AtomicInteger(1);private final String namePrefix;NamedThreadFactory() {SecurityManager s = System.getSecurityManager();group = (s != null) ? s.getThreadGroup() :Thread.currentThread().getThreadGroup();namePrefix = "MyTaskPool-" + poolNumber.getAndIncrement() + "-thread-";}@Overridepublic Thread newThread(Runnable r) {Thread t = new Thread(group, r,namePrefix + threadNumber.getAndIncrement(),0);if (t.isDaemon())t.setDaemon(false);if (t.getPriority() != Thread.NORM_PRIORITY)t.setPriority(Thread.NORM_PRIORITY);return t;}
}
//我们提交了20个任务到线程池。由于工作队列容量有限（10），当队列满后会尝试增加线程直到达到最大线程数（4）。
//如果在达到最大线程数后仍有新的任务提交，将根据指定的拒绝策略处理这些任务。
// 在本例中，我们选择了 CallerRunsPolicy，这意味着超出线程池处理能力的任务将会由调用者线程（主线程）直接执行。
//执行结果
//Task 0 is running by MyTaskPool-1-thread-1
// Task 14 is running by main
// Task 1 is running by MyTaskPool-1-thread-2
// Task 13 is running by MyTaskPool-1-thread-4
// Task 12 is running by MyTaskPool-1-thread-3
// Task 12 finished
// Task 1 finished
// Task 0 finished
// Task 13 finished
// Task 14 finished
// Task 4 is running by MyTaskPool-1-thread-3
// Task 19 is running by main
// Task 5 is running by MyTaskPool-1-thread-4
// Task 3 is running by MyTaskPool-1-thread-1
// Task 2 is running by MyTaskPool-1-thread-2
// Task 5 finished
// Task 4 finished
// Task 19 finished
// Task 3 finished
// Task 8 is running by MyTaskPool-1-thread-1
// Task 2 finished
// Task 9 is running by MyTaskPool-1-thread-2
// Task 7 is running by MyTaskPool-1-thread-3
// Task 6 is running by MyTaskPool-1-thread-4
// Task 8 finished
// Task 10 is running by MyTaskPool-1-thread-1
// Task 6 finished
// Task 9 finished
// Task 7 finished
// Task 15 is running by MyTaskPool-1-thread-2
// Task 11 is running by MyTaskPool-1-thread-4
// Task 16 is running by MyTaskPool-1-thread-3
// Task 10 finished
// Task 17 is running by MyTaskPool-1-thread-1
// Task 11 finished
// Task 15 finished
// Task 16 finished
// Task 18 is running by MyTaskPool-1-thread-4
// Task 17 finished
// Task 18 finished
// 所有任务已完成，线程池已关闭
示例2：
package org.springblade.test;import lombok.extern.slf4j.Slf4j;import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;@Slf4j
public class Test {@org.junit.jupiter.api.Testpublic void ThreadPoolExecutorExample() {// 定义核心线程数、最大线程数、空闲线程存活时间以及时间单位int corePoolSize = 5;int maximumPoolSize = 10;long keepAliveTime = 60; // 60秒TimeUnit unit = TimeUnit.SECONDS;// 创建一个有界的LinkedBlockingQueue作为任务队列，容量为20BlockingQueue<Runnable> workQueue = new LinkedBlockingQueue<>(20);// 创建线程池ThreadPoolExecutor executor = new ThreadPoolExecutor(corePoolSize,maximumPoolSize,keepAliveTime,unit,workQueue);// 提交任务到线程池for (int i = 0; i < 30; i++) {final int taskId = i;Runnable worker = () -> {System.out.println("Task " + taskId + " is running by " + Thread.currentThread().getName());try {Thread.sleep(1000); // 模拟耗时操作} catch (InterruptedException e) {e.printStackTrace();}System.out.println("Task " + taskId + " finished");};executor.execute(worker);}// 关闭线程池（这里没有立即关闭，而是等待所有任务执行完毕）executor.shutdown();while (!executor.isTerminated()) {// 等待所有任务执行完毕}System.out.println("所有任务已完成，线程池已关闭");}
}//执行结果
// Task 0 is running by pool-1-thread-1
// Task 1 is running by pool-1-thread-2
// Task 3 is running by pool-1-thread-4
// Task 2 is running by pool-1-thread-3
// Task 4 is running by pool-1-thread-5
// Task 25 is running by pool-1-thread-6
// Task 26 is running by pool-1-thread-7
// Task 27 is running by pool-1-thread-8
// Task 29 is running by pool-1-thread-10
// Task 28 is running by pool-1-thread-9
// Task 2 finished
// Task 0 finished
// Task 3 finished
// Task 5 is running by pool-1-thread-1
// Task 6 is running by pool-1-thread-4
// Task 7 is running by pool-1-thread-3
// Task 1 finished
// Task 8 is running by pool-1-thread-2
// Task 4 finished
// Task 9 is running by pool-1-thread-5
// Task 25 finished
// Task 10 is running by pool-1-thread-6
// Task 27 finished
// Task 28 finished
// Task 26 finished
// Task 13 is running by pool-1-thread-7
// Task 29 finished
// Task 14 is running by pool-1-thread-10
// Task 11 is running by pool-1-thread-8
// Task 12 is running by pool-1-thread-9
// Task 7 finished
// Task 15 is running by pool-1-thread-3
// Task 5 finished
// Task 16 is running by pool-1-thread-1
// Task 6 finished
// Task 17 is running by pool-1-thread-4
// Task 8 finished
// Task 18 is running by pool-1-thread-2
// Task 9 finished
// Task 19 is running by pool-1-thread-5
// Task 10 finished
// Task 20 is running by pool-1-thread-6
// Task 12 finished
// Task 21 is running by pool-1-thread-9
// Task 14 finished
// Task 11 finished
// Task 22 is running by pool-1-thread-8
// Task 23 is running by pool-1-thread-10
// Task 13 finished
// Task 24 is running by pool-1-thread-7
// Task 15 finished
// Task 17 finished
// Task 16 finished
// Task 18 finished
// Task 19 finished
// Task 20 finished
// Task 23 finished
// Task 22 finished
// Task 24 finished
// Task 21 finished
)
