Question

这是对Concurrency

上的Java教程的代码的修改

package threads;

public class SimpleThreads {
 static void threadMessage(String msg) {
  String threadName = Thread.currentThread().getName();
  System.out.format("%s: %s%n", threadName,msg);
 }
 private static class MessageLoop implements Runnable{

  @Override
  public void run() {
   // TODO Auto-generated method stub
   String[] importantInfo= {"apple","bat","chlorine","dog","egg","fog","gun"};
   try {
    for(int i=0;i<importantInfo.length;i++) {
     Thread.sleep(4000);
     threadMessage(importantInfo[i]);
    }
   }catch(InterruptedException ie) {
    threadMessage("i wasn't done");
   }
     }
 }
 /**
  * @param args
  */
 public static void main(String[] args) throws InterruptedException{
  // TODO Auto-generated method stub
  long patience = 100;
  if(args.length > 0)
   try {
    patience = Long.parseLong(args[0]) * 1000;
   }catch(NumberFormatException nfe) {
    System.err.println("argument must be a integer");
    System.exit(1);
   }
  threadMessage("starting message loop thread");
  long startTime = System.currentTimeMillis();
  Thread t = new Thread(new MessageLoop());
  t.start();

  threadMessage("waiting for messageloop thread to finish");
  while(t.isAlive()) {
   threadMessage("still waiting...");
   //t.join(1000);
   if(((System.currentTimeMillis() - startTime) > patience) && t.isAlive()) {
    threadMessage("tired of waiting");
    t.interrupt();
    //t.join();
   }
  }
  threadMessage("finally");
 }

}

这是输出

main: starting message loop thread
main: waiting for messageloop thread to finish
main: still waiting...
main: still waiting...
...(repeats about 100 times)
main: still waiting...
main: still waiting...
main: still waiting...
main: still waiting...
main: tired of waiting
main: still waiting...
main: tired of waiting
main: still waiting...
main: tired of waiting
main: still waiting...
main: tired of waiting
main: still waiting...
main: tired of waiting
Thread-0: i wasn't done
main: finally

我预计在第一次（并且据说只有）main: tired of waiting之后，我会看到Thread-0: i wasn't done，但main: tired of waiting会出现5次 - 为什么会这样？

Answer 1

Thread.Interrupt（）只是向目标线程发送一个中断（信号/异常）;它不会立即杀死它。

此外，在发送中断与目标线程接收和处理中断之间可能存在延迟;不保证上下文切换是立即的。

您可以通过执行某种形式的阻塞操作（例如I / O或休眠）或通过调用Thread.yield（）来鼓励（但不强制）JVM更快地进行上下文切换。

Answer 2

Thread.interrupt()不会杀死或中断线程它只会中断某些方法，如睡眠，等待，加入，可中断通道上的阻塞I / O或阻塞的选择器。否则它只是设置线程的中断标志，由你来测试这个标志如果你在上面的代码中删除了睡眠，那么中断将没有明显的效果。

线程将（可能）被中断几次，因为实际的线程（主循环）继续运行，直到系统变为中断的线程。中断后你可以添加一个sleep（）或yield（）（join（），如图所示，也应该工作）以允许中断的线程运行

    threadMessage("tired of waiting");
    t.interrupt();
    t.yield();

另见documentation of interrupt

为什么Thread.interrupt（）表现得像这样？

2 个答案: