Executors创建线程池的正确方法及源码分析

java.util.concurrent.ExecutorService;
java.util.concurrent.Executors;
这两个包可以用来创建线程池，具体的方法如下：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


//Excutors 工具类、3大方法
public class ThreadPoolTest {
    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newSingleThreadExecutor();        //单个线程
//        ExecutorService threadPool  = Executors.newFixedThreadPool(5);       //固定大小的线程池
//       ExecutorService threadPool  = Executors.newCachedThreadPool();        //可变大小的线程池
        try {
            for (int i=0;i<100;i++){
                threadPool.execute(()->{
                    System.out.println(Thread.currentThread().getName()+"  ok");
                });
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
           threadPool.shutdown();
        }
    }

}

 public static ExecutorService newSingleThreadExecutor() {
        return new FinalizableDelegatedExecutorService
            (new ThreadPoolExecutor(1, 1,
                                    0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>()));
    }
   public static ExecutorService newFixedThreadPool(int nThreads) {
     return new ThreadPoolExecutor(nThreads, nThreads,
                                   0L, TimeUnit.MILLISECONDS,
                                   new LinkedBlockingQueue<Runnable>());
 }
   public static ExecutorService newCachedThreadPool() {
       return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                     60L, TimeUnit.SECONDS,
                                     new SynchronousQueue<Runnable>());
   }

这三个方法底层都调用了以下方法：

  public ThreadPoolExecutor(int corePoolSize,//核心线程池的大小
                              int maximumPoolSize, //最大核心线程池大小
                              long keepAliveTime, //超时释放时间
                              TimeUnit unit,//超时释放单位
                              BlockingQueue<Runnable> workQueue) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), defaultHandler);
    }

正确的写法为：

import java.util.concurrent.*;


//Excutors 工具类、3大方法
public class ThreadPoolTest {
    public static void main(String[] args) {
//        ExecutorService threadPool = Executors.newSingleThreadExecutor();        //单个线程
//        ExecutorService threadPool  = Executors.newFixedThreadPool(5);       //固定大小的线程池
//       ExecutorService threadPool  = Executors.newCachedThreadPool();        //可变大小的线程池
        ExecutorService threadPool =new ThreadPoolExecutor(
                2,
                5,
                3,
                TimeUnit.SECONDS,
                new LinkedBlockingDeque<>(3),
                Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.AbortPolicy()
        );
        try {
            //最大承载数 = maximunPoolSize+ Deque capacity
            for (int i=0;i<9;i++){
                threadPool.execute(()->{
                    System.out.println(Thread.currentThread().getName()+"  ok");
                });
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            threadPool.shutdown();
        }
    }

}