Java中线程池自定义实现详解

public enum State {
    
    NEW, // 新建

    
    RUNNABLE, // 运行中

    
    BLOCKED, // 阻塞

    
    WaiTING, // 等待

    
    TIMED_WAITING, // 定时等待

    
    TERMINATED; // 结束状态
}

public void testThreadPool() {

    ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 3, 10L, TimeUnit.SECONDS, new ArrayBlockingQueue(3));
    threadPoolExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
    for (int i=0; i<5; i++) {

        threadPoolExecutor.submit(new Runnable() {
            @Override
            public void run() {
                ThreadUtils.doSleep(10000L);
                System.out.println(Thread.currentThread().getName() + "--运行");
            }
        });
    }

    threadPoolExecutor.shutdown();
}

while (task != null || (task = getTask()) != null) {
    w.lock();
    // If pool is stopping, ensure thread is interrupted;
    // if not, ensure thread is not interrupted.  This
    // requires a recheck in second case to deal with
    // shutdownNow race while clearing interrupt
    if ((runStateAtLeast(ctl.get(), STOP) ||
         (Thread.interrupted() &&
          runStateAtLeast(ctl.get(), STOP))) &&
        !wt.isInterrupted())
        wt.interrupt();
    try {
        beforeExecute(wt, task);
        Throwable thrown = null;
        try {
            task.run();
        } catch (RuntimeException x) {
            thrown = x; throw x;
        } catch (Error x) {
            thrown = x; throw x;
        } catch (Throwable x) {
            thrown = x; throw new Error(x);
        } finally {
            afterExecute(task, thrown);
        }
    } finally {
        task = null;
        w.completedTasks++;
        w.unlock();
    }
}

package com.cz.lock.distributed.impl.Redis;

import java.util.List;
import java.util.concurrent.*;


public class JefThreadPoolExecutor extends AbstractExecutorService {

    
    private final BlockingQueue<Worker> workers = new LinkedBlockingQueue<Worker>();

    private static int coreThreadCount = 5;
    private static int maxThreadCount = 10;
    private static int defaultQueueSize = maxThreadCount * 5;
    private static BlockingQueue<Runnable> blockingQueue = new ArrayBlockingQueue<Runnable>(defaultQueueSize);
    
    JefThreadPoolExecutor() {
        this(coreThreadCount, maxThreadCount, blockingQueue);
    }
    
    JefThreadPoolExecutor(int coreThreadCount, int maxThreadCount, BlockingQueue blockingQueue) {
        this.blockingQueue = blockingQueue;
        this.coreThreadCount = coreThreadCount;
        this.maxThreadCount = maxThreadCount;
    }

    @Override
    public void shutdown() {

    }

    @Override
    public List<Runnable> shutdownNow() {
        return null;
    }

    @Override
    public boolean isshutdown() {
        return false;
    }

    @Override
    public boolean isTerminated() {
        return false;
    }

    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
        return false;
    }

    @Override
    public void execute(Runnable command) {

        int currentWorkCount = workers.size(); // 当前创建的线程总数
        if (currentWorkCount < coreThreadCount) { // 如果当前线程总数小于核心线程数，则新建线程
            Worker worker = new Worker(command);
            final Thread thread = worker.thread;
            thread.start();
            addWorker(worker);
            return;
        }
        if (!blockingQueue.offer(command) && currentWorkCount <= maxThreadCount) { // 队列可以正常放入则返回true，如果满了返回false
            // 队列如果满了，需要创建新的线程
            Worker worker = new Worker(command);
            final Thread thread = worker.thread;
            thread.start();
            addWorker(worker);
            return;
        } else if (currentWorkCount > maxThreadCount){
            System.out.println("线程池满了....没有多余的线程了");
        }


    }

    public void addWorker(Worker worker) {
        workers.add(worker);
    }

    public Runnable getTask() {
        Runnable poll = blockingQueue.poll();
        return poll;
    }

    public void runWorker(Worker worker) {

        Runnable task = worker.firstTask; // 获取到new Worker时传入的那个任务，并在下面运行
        if (task != null) {
            task.run();
        }
        worker.firstTask = null;
        // 循环从队列中获取任务处理
        while((task = getTask()) != null) {
            task.run();
        }
    }

    
    private class Worker implements Runnable{

        volatile int state = 0;
        public Runnable firstTask;
        final Thread thread;
        public Worker(Runnable firstTask) {
            this.firstTask = firstTask;
            thread = new Thread(this);
        }

        @Override
        public void run() {
            runWorker(this);
        }
    }
}

public static void singleThreadPoolExecutor() {
    JefThreadPoolExecutor jefThreadPoolExecutor = new JefThreadPoolExecutor();
    for (int i=0; i<10; i++) {
        jefThreadPoolExecutor.execute(new Runnable() {
            @Override
            public void run() {
                System.out.println(Thread.currentThread().getName() + "--运行");
            }
        });
    }
}


public static void diyThreadPoolExecutor() {
    JefThreadPoolExecutor jefThreadPoolExecutor = new JefThreadPoolExecutor(2, 10, new ArrayBlockingQueue(50));

    for (int i=0; i<500; i++) {
        jefThreadPoolExecutor.execute(new Runnable() {
            @Override
            public void run() {
                System.out.println(Thread.currentThread().getName() + "--运行");
            }
        });
    }
}