在ThreadPoolExector#shutdown的文档中,它说：

This method does not wait for previously submitted tasks to complete execution

那是什么意思？

因为我认为已经提交的排队任务可能无法完成,但事实并非如此;请参阅此示例代码,该代码在完成所有提交的任务之前调用shutdown：

package example;

import java.util.concurrent.*;

public class ExecutorTest {

    public static void main(String ... args) {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        for (int i = 0; i < 10; i++) {
            final int count = i;
            executorService.execute(() -> {
                System.out.println("starting " + count);
                try {
                    Thread.sleep(10000L);
                } catch (InterruptedException e) {
                    System.out.println("interrupted " + count);
                }
                System.out.println("ended " + count);
            });
        }
        executorService.shutdown();         
    }    
}

哪个印刷品：

C:\>java -cp . example.ExecutorTest
starting 0
starting 2
starting 1
ended 2
ended 0
starting 3
starting 4
ended 1
starting 5
ended 3
ended 5
ended 4
starting 7
starting 6
starting 8
ended 7
ended 6
ended 8
starting 9
ended 9

C:\>

在这个例子中,很明显提交的任务完成了执行.我使用Oracle和IBM JDK在JDK8上运行它并获得相同的结果.

那么文档试图说的是什么？或者是否有人为shutdownNow写了这个并将其剪切并粘贴到文档中以便无意中关闭？

解决方法:

在ThreadPoolExector#shutdown的文档中,还有一句话：

This method does not wait for previously submitted tasks to complete
execution. Use awaitTermination to do that.

在此上下文中,它表示调用者线程不会等待先前提交的任务完成执行.换句话说,shutdown()不会阻止调用者线程.

如果您确实需要阻止调用者线程,请使用ThreadPoolExector#awaitTermination(long timeout, TimeUnit unit)：

Blocks until all tasks have completed execution after a shutdown
request, or the timeout occurs, or the current thread is interrupted,
whichever happens first.