1、基本概念

Java线程需要经过线程的创建，调用和销毁整个过程，频繁的创建和销毁会大大影响性能，所以引入的线程池：
好处：

1. 提升性能：线程池能独立负责线程的创建、维护和分配
2. 线程管理：每个Java线程池会保持一些基本的线程统计信息，对线程进行有效管理

2、JUC线程池架构

JUC指的是Java的并发工具包

1. Executor

Executor提供了execute()接口，用来执行已提交的Runnable目标实例，它只有1个方法：

void execute(Runnable command)

2. ExecutorService

继承于Executor.Java，异步目标任务的“执行者服务”接口，对外提供异步任务的接收服务

* @param task the task to submit
* @param <T> the type of the task's result
* @return a Future representing pending completion of the task
* @throws RejectedExecutionException if the task cannot be
*         scheduled for execution
* @throws NullPointerException if the task is null
*/
<T> Future<T> submit(Callable<T> task);//向线程池提交单个异步任务

//想线程池提交批量异步任务
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
                                  long timeout, TimeUnit unit)
        throws InterruptedException;

3. AbstractExecutorService

抽象类，实现了ExecutorService

4. ThreadPoolExecutor

线程池实现类，继承于AbstractExecutorService，JUC线程池的核心实现类

5. ScheduledExecutorService

继承于ExecutorService。它是一个可以完成“延时”和“周期性”任务的调度线程池接口

6. ScheduledThreadPoolExecutor

继承于ThreadPoolExecutor，实现了ExecutorService中延时执行和周期执行等抽象方法

7. Executors

静态工厂类，它通过静态工厂方法返回ExecutorService、ScheduledExecutorService等线程池示例对象

3. Executors创建线程的4种方法

1. newSingleThreadExecutor创建“单线程化线程池”

package threadpool;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicInteger;

public class CreateThreadPollDemo {
    public static final int SLEEP_GAP=1000;
    static class TargetTask implements Runnable{
        static AtomicInteger taskNo=new AtomicInteger(1);
        private String taskName;
        public TargetTask()
        {
            taskName="task-"+taskNo;
            taskNo.incrementAndGet();
        }
        public void run()
        {
            System.out.println("task:"+taskName+" is doing...");
            try {
                Thread.sleep(SLEEP_GAP);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("task:"+taskName+" end...");
        }
    }
    public static void main(String[] args) {
        ExecutorService pool=Executors.newSingleThreadExecutor();
        for(int i=0;i<3;i++)
        {
            pool.execute(new TargetTask());
            pool.submit(new TargetTask());
        }
        pool.shutdown();
    }
 
}

Java线程池（超详细）