自定義實現newFixedThreadPool

自定義實現MyFixedThreadPool

自己想深入研究一下線程池的實現，所以自定義實現一下，首先考慮，既然線程池的初始化需要一個任務隊列與線程集合，具體的代碼如下：

package com.bdcloud.threadpool;

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

/***
 * 自定義線程池 newFixedThreadPool
 */
public class MyFixedThreadPool {

    //存放任務
    LinkedBlockingQueue<Runnable> queue;

    //存放的工作線程
    List<Worker> workers;

    public MyFixedThreadPool(int queueSize,int workSize){

        if (queueSize<=0 || workSize<=0){
            throw new IllegalArgumentException("參數傳遞錯誤");
        }
        //初始化工作集合於工作隊列
        this.queue = new LinkedBlockingQueue<>(queueSize);
        this.workers = Collections.synchronizedList(new ArrayList<>(workSize));
        //初始化所有的工作線程
        for (int i = 0; i < workSize; i++) {
            Worker worker = new Worker(this);
            worker.start();
            this.workers.add(worker);
        }
    }

    //定義工作類
    public static  class Worker extends Thread{

        private MyFixedThreadPool threadPool;

        public Worker(MyFixedThreadPool threadPool){
            this.threadPool = threadPool;
        }

        @Override
        public void run() {
            while (this.threadPool.isWorking||this.threadPool.queue.size()>0){
                Runnable take = null;
                try {
                    //從工作隊列取任務並執行
                    if (this.threadPool.isWorking){
                        take = threadPool.queue.take();
                    }else {
                        take = threadPool.queue.poll();
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                if (take!=null){
                    take.run();
                    System.out.println("當前的線程"+Thread.currentThread().getName()+"執行完畢");
                }
            }
        }
    }

    /**
     * 提交任務
     * @param runnable
     * @return
     */
    public boolean submit(Runnable runnable){
        if (this.isWorking){
            return this.queue.offer(runnable);
        }
        return false;
    }
    //判斷線程池是否在運行
    private volatile  boolean isWorking = true;

    /**
     * 關閉線程池
     * 1.就是線程池停止接收任務
     * 2.若任務隊列中還有數據，則繼續取出並執行
     * 3.中斷變量設置後，取任務的時候就不必要阻塞的取
     * 4.一旦任務阻塞，我們就應該去中斷它
     */
    private void shutDown(){
        this.isWorking = false;
        for (Thread thread:workers) {
        if (thread.getState().equals(Thread.State.BLOCKED))
            thread.interrupt();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        MyFixedThreadPool pool = new MyFixedThreadPool(6,3);

        //向線程池提交6個任務
        for (int i = 0; i < 6; i++) {
        pool.submit(new Runnable() {
            @Override
            public void run() {
                System.out.println("提交了一個線程");
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        }
        //關閉線程池
        pool.shutDown();
    }
}