Java 线程池的使用

文章主要介绍 ThreadPoolExecutor 线程池的简单使用和相关注意事项

public class ThreadPoolTest {

    public static void main(String[] args) {

        /// 创建线程池: 核心数量5个,最大数量10个,当线程在200毫秒没内没反应关闭线程,缓存列队5个
        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                5, 10, 200, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(5));
        for(int i = 0; i < 20; i++) {
            TaskTest task = new TaskTest(1000000 + i);
            executor.execute(task);
            System.out.println(
                    "执行中的线程数量:" + executor.getPoolSize() +
                    ",等待执行的任务数目:" + executor.getQueue().size() +
                    ",执行完毕的任务数目:" + executor.getCompletedTaskCount());
        }
        executor.shutdown();

        /// 从运行日志可看出,池中线程数量本来是5个,在缓存队列满后逐步加到了10个,但再往后就加不进去了,如果再加就会报错:
        ///     Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task com.hui.threadPool.TaskTest@19bb089b rejected from java.util.concurrent.ThreadPoolExecutor@4563e9ab[Running, pool size = 10, active threads = 10, queued tasks = 5, completed tasks = 0]
        //	    at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2047)
        //	    at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:823)
        //	    at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1369)
        //	    at com.hui.threadPool.ThreadPoolTest.main(ThreadPoolTest.java:15)


        /// 如果想要不断添加到缓存队列而不报错,可以将缓存队列设置为new LinkedBlockingQueue<>(),此时最大数量将失效 !!!
        ThreadPoolExecutor executor2 = new ThreadPoolExecutor(
                5, 10, 200, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<>());
    }
}

任务类为:

public class TaskTest implements Runnable {

    private int taskId;

    public TaskTest(int id) {
        this.taskId = id;
    }

    @SuppressWarnings("static-access")
    @Override
    public void run() {
        System.out.println("开始执行任务 " + taskId);
        try {
            Thread.currentThread().sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("任务 " + taskId + "执行完毕");
    }
}
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