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线程池是重点也是难点, 结合知识点较多, 一番理解后写出简单的线程池实现

package edu.cxf.dongnao;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

/**
 * 綫程池.
 */
public class KeithTreadPool {

    // 1.任務倉庫
    private BlockingQueue<Runnable> blockingQueue;
    // 2.服務人員集合
    private List<Thread> workers;

    // 關閉標識
    private volatile boolean isWorking = true;

    // 3.服務人員
    class Worker extends Thread {
        private KeithTreadPool keithTreadPool;

        public Worker(KeithTreadPool keithTreadPool) {
            this.keithTreadPool = keithTreadPool;
        }

        @Override
        public void run() {
            while (this.keithTreadPool.isWorking || this.keithTreadPool.blockingQueue.size() > 0) {
                Runnable task = null;
                try {
                    if (this.keithTreadPool.isWorking) {
                        task = this.keithTreadPool.blockingQueue.take();
                    } else {
                        task = this.keithTreadPool.blockingQueue.poll();
                    }

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                if (task != null) {
                    task.run();
                    System.out.println(Thread.currentThread().getName() + "完成執行任務！");
                }
            }
        }
    }

    // 4.初始化倉庫和服務組織大小
    public KeithTreadPool(int poolSize, int taskSize) {
        if (poolSize <= 0 || taskSize <= 0) {
            throw new IllegalArgumentException("參數錯誤");
        }

        this.blockingQueue = new LinkedBlockingQueue<>(taskSize);
        this.workers = Collections.synchronizedList(new ArrayList<>());
        for (int i = 0; i < poolSize; i++) {
            Worker worker = new Worker(this);
            worker.start();
            workers.add(worker);
        }
    }


    // 5.前臺接待引導客人排隊
    public boolean submit(Runnable runnable) {
        if (this.isWorking) {
            return this.blockingQueue.offer(runnable);
        } else {
            return false;
        }
    }

    // 6.關閉
    // a.關閉時候--前臺--不再接待客人
    // b.關閉時候--排隊--執行完
    // c.關閉時候--服務人員--再去拿客人時就不能阻塞
    // d.關閉時候--服務人員已經阻塞--中斷他
    //
    public void shutdown() {
        // 設置關閉標識
        this.isWorking = false;

        for (Thread worker : workers) {
            if (worker.getState().equals(Thread.State.BLOCKED) || worker.getState().equals(Thread.State.WAITING)) {
                worker.interrupt();
            }
        }
    }

    public static void main(String[] args) {
        KeithTreadPool keithTreadPool = new KeithTreadPool(4, 20);

        for (int i = 0; i < 20; i++) {
            final int current = i;
            keithTreadPool.submit(new Runnable() {
                @Override
                public void run() {
                    System.out.println("計算第" + current + "次過程");

                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            });
        }

        keithTreadPool.shutdown();
    }
}

附 : 一组图片帮助理解