线程池几个重要参数

public ThreadPoolExecutor(    int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue,
                              ThreadFactory threadFactory,
                              RejectedExecutionHandler handler)

int corePoolSize 默认工作线程数
int maximumPoolSize 最大工作线程数
long keepAliveTime 线程存活时间
TimeUnit unit 线程存活的时间单位
BlockingQueue workQueue 阻塞队列
ThreadFactory threadFactory 线程默认创建工厂
RejectedExecutionHandler handler 线程拒绝策略
线程拒绝策略有四种：
1直接拒绝 超过最大线程数+阻塞的队列数将会报
RejectedExecutionException
如一下代码

public class test1 {
    public static void main(String[] args) {
        ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.AbortPolicy());
        try{
            for(int i=0;i<=15;i++){
                executorService.execute(
                        ()->{
                            System.out.println(Thread.currentThread().getName()+"\t执行业务");
                        }
                );
            }

        }catch (Exception e){
            System.out.println("抛出异常");
            e.printStackTrace();
        }
        finally {
            executorService.shutdown();
        }

    }
}

java线程池学习（自定义线程池）_抛出异常


源码如下

java线程池学习（自定义线程池）_抛出异常_02


二 回退策略

将执行的任务回退给交付这个任务的人

如main线程

ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.CallerRunsPolicy());

java线程池学习（自定义线程池）_System_03


三抛弃策略

将多余的任务抛弃

//修改代码如下
ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.DiscardPolicy());

最后没有执行100个请求

java线程池学习（自定义线程池）_工作线程_04


四抛弃最老的策略

将最老的线程抛弃，最后也没能执行100个请求

public class test1 {
    public static void main(String[] args) {
        /*
        ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.AbortPolicy());*/
        /**
        ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.CallerRunsPolicy());**/
        /**
        ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.DiscardPolicy());**/
        ExecutorService executorService=new  ThreadPoolExecutor(3,8,
                2, TimeUnit.SECONDS,new LinkedBlockingDeque<>(3)
                , Executors.defaultThreadFactory(),
                new ThreadPoolExecutor.DiscardOldestPolicy());
        try{
            for(int i=0;i<=100;i++){
                executorService.execute(
                        ()->{

                            try {

                                TimeUnit.SECONDS.sleep(3);
                                System.out.println(Thread.currentThread().getName()+"\t执行业务");
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                        }
                );
            }

        }catch (Exception e){
            System.out.println("抛出异常");
            e.printStackTrace();
        }
        finally {
            executorService.shutdown();
        }

    }
}

java线程池学习（自定义线程池）_工作线程_05