Java多线程之线程池七个参数详解

 public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              ThreadFactory threadFactory,
                              RejectedExecutionHandler handler) {
        if (corePoolSize < 0 ||
            maximumPoolSize <= 0 ||
            maximumPoolSize < corePoolSize ||
            keepAliveTime < 0)
            throw new IllegalArgumentException();
        if (workQueue == null || threadFactory == null || handler == null)
            throw new NullPointerException();
        this.acc = System.getSecurityManager() == null ?
                null :
                AccessController.getContext();
        this.corePoolSize = corePoolSize;
        this.maximumPoolSize = maximumPoolSize;
        this.workQueue = workQueue;
        this.keepAliveTime = unit.toNanos(keepAliveTime);
        this.threadFactory = threadFactory;
        this.handler = handler;
    }

public class ThreadPoolExecutor extends AbstractExecutorService {
    private final BlockingQueue<Runnable> workQueue;
    private volatile ThreadFactory threadFactory;
    private volatile RejectedExecutionHandler handler;
    private volatile long keepAliveTime;
    // 是否允许核心线程被回收
    private volatile boolean allowCoreThreadTimeOut;
    private volatile int corePoolSize;
    private volatile int maximumPoolSize;
}

TimeUnit.NANOSECONDS
TimeUnit.MICROSECONDS
TimeUnit.MILLISECONDS // 毫秒
TimeUnit.SECONDS
TimeUnit.MINUTES
TimeUnit.HOURS
TimeUnit.DAYS

  /**
     * The default thread factory
     */
    static class DefaultThreadFactory 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;
 
        DefaultThreadFactory() {
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() :
                                  Thread.currentThread().getThreadGroup();
            namePrefix = "pool-" +
                          poolNumber.getAndIncrement() +
                         "-thread-";
        }
 
        public 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;
        }
    }

  /**
     * The default rejected execution handler
     */
    private static final RejectedExecutionHandler defaultHandler = new AbortPolicy();
 
    public static class AbortPolicy implements RejectedExecutionHandler {
        /**
         * Creates an {@code AbortPolicy}.
         */
        public AbortPolicy() { }
 
        /**
         * Always throws RejectedExecutionException.
         *
         * @param r the runnable task requested to be executed
         * @param e the executor attempting to execute this task
         * @throws RejectedExecutionException always
         */
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            throw new RejectedExecutionException("Task " + r.toString() +
                                                 " rejected from " +
                                                 e.toString());
        }
    }

import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
 
/**
 * 线程池工厂工具
 *
 * @author 向振华
 * @date 2021/04/11 10:24
 */
public class ThreadPoolFactory {
 
    /**
     * 生成固定大小的线程池
     *
     * @param threadName 线程名称
     * @return 线程池
     */
    public static ExecutorService createFixedThreadPool(String threadName) {
        AtomicInteger threadNumber = new AtomicInteger(0);
        return new ThreadPoolExecutor(
                // 核心线程数
                desiredThreadNum(),
                // 最大线程数
                desiredThreadNum() * 2,
                // 空闲线程存活时间
                60L,
                // 空闲线程存活时间单位
                TimeUnit.SECONDS,
                // 工作队列
                new ArrayBlockingQueue<>(1024),
                // 线程工厂
                new ThreadFactory() {
                    @Override
                    public Thread newThread(Runnable r) {
                        return new Thread(r, threadName + "-" + threadNumber.getAndIncrement());
                    }
                },
                // 拒绝策略
                new RejectedExecutionHandler() {
                    @Override
                    public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
                        if (!executor.isShutdown()) {
                            try {
                                //尝试阻塞式加入任务队列
                                executor.getQueue().put(r);
                            } catch (Exception e) {
                                //保持线程的中断状态
                                Thread.currentThread().interrupt();
                            }
                        }
                    }
                });
    }
 
    /**
     * 理想的线程数，使用 2倍cpu核心数
     */
    public static int desiredThreadNum() {
        return Runtime.getRuntime().availableProcessors() * 2;
    }
}