ThreadPoolExecutor线程池的使用及原理（一篇就够）

缺乏、安全感 2023-01-17 02:23 78阅读 0赞

线程池原理：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MzYwMTM1OQ_size_16_color_FFFFFF_t_70]

package com.cy.java.api.thread;
    
    import java.util.concurrent.*;
    import java.util.concurrent.atomic.AtomicInteger;
    //JUC
    
    public class ThreadPoolTests { 
        public static void main(String[] args) { 
        
        	//核心线程，核心线程满了，放入队列，队列满了开启再新线程。
            int corePoolSize=2;
            
            //最大线程数（核心线程+新线程），最大线程数、队列数都满了，默认抛异常
            int maximumPoolSize=3;
            
            //线程池中空闲线程等待工作的超时时间
            int keepAliveTime=60;
            
            //时间颗粒度转换(例如keepAliveTime默认单位为毫秒，转换成秒)
            TimeUnit unit=TimeUnit.SECONDS;
            
            //任务队列,存储要执行的任务，最大队列数设为1
            BlockingQueue<Runnable> workQueue=new ArrayBlockingQueue<>(1);
            
            //定义执行器
            RejectedExecutionHandler handler=
            //new ThreadPoolExecutor.AbortPolicy();//不能执行任务时，抛出异常
              new ThreadPoolExecutor.CallerRunsPolicy();//由调用者去执行
    
            //创建线程的工厂
            ThreadFactory threadFactory=new ThreadFactory() { 
            	//定义线程名
                private String prefix="db-service-thread-";
                //生成自增长数
                private AtomicInteger atomicInteger=new AtomicInteger(0);
                @Override
                public Thread newThread(Runnable task) { 
                    return new Thread(task,prefix+atomicInteger.incrementAndGet());
                }
            };
    
              
            //构建线程池对象
            ThreadPoolExecutor threadPool= new ThreadPoolExecutor(
                            corePoolSize,
                            maximumPoolSize,
                            keepAliveTime,
                            unit,
                            workQueue,
                            threadFactory,
                            handler);
    
    
    //设置休眠时间测试允许结果。核心线程数2，最大线程树3，最大队列1，超出最大限线程数时，由调用者去执行。
            threadPool.execute(new Runnable() { //task
                @Override
                public void run() { 
                    String tName=Thread.currentThread().getName();
                    System.out.println(tName+"->execute->task1");
                    try{ Thread.sleep(5000);}catch (Exception e){ }
                }
            });
            threadPool.execute(new Runnable() { //task
                @Override
                public void run() { 
                    String tName=Thread.currentThread().getName();
                    System.out.println(tName+"->execute->task2");
                    try{ Thread.sleep(5000);}catch (Exception e){ }
                }
            });
            threadPool.execute(new Runnable() { //task
                @Override
                public void run() { 
                    String tName=Thread.currentThread().getName();
                    System.out.println(tName+"->execute->task3");
                }
            });
            threadPool.execute(new Runnable() { //task
                @Override
                public void run() { 
                    String tName=Thread.currentThread().getName();
                    System.out.println(tName+"->execute->task4");
                    try{ Thread.sleep(5000);}catch (Exception e){ }
                }
            });
            threadPool.execute(new Runnable() { //task
                @Override
                public void run() { 
                    String tName=Thread.currentThread().getName();
                    System.out.println(tName+"->execute->task5");
                    try{ Thread.sleep(5000);}catch (Exception e){ }
                }
            });
    
        }
    }
    
    /*运行结果： db-service-thread-1->execute->task1 db-service-thread-2->execute->task2 db-service-thread-3->execute->task4 main->execute->task5 db-service-thread-2->execute->task3 */

线程溢出时出错：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MzYwMTM1OQ_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MzYwMTM1OQ_size_16_color_FFFFFF_t_70]: /images/20221022/3bc10976233a45bfaefd00ad35b13a8e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MzYwMTM1OQ_size_16_color_FFFFFF_t_70 1]: /images/20221022/99d3732ccebf46d588c25f7bf1b0a876.png