java - java中线程setDeaemon的困惑

Question

根据java当setDaemon设置为true时

it does not prevent the JVM from exiting when the program finishes but the thread is still running. An example for a daemon thread is the garbage collection.

从下面的代码示例中，当setDaemon设置为true时，主线程创建的线程停止执行，实际上它应该继续运行。当setDaemon设置为false时，即使主线程退出，子线程也会打印i的值。请澄清我的疑问。

public class DeamonSample implements Runnable
{
      public void run()
      {
            try 
{
System.out.println("T1 started...");

                  for (int i=0;i<1000;i++)
                  {
                        TimeUnit.SECONDS.sleep(1);
                        System.out.print(i+" ");
                  }
            } 
            catch (InterruptedException e) 
            {
                  // TODO Auto-generated catch block
                  e.printStackTrace();
            }
            finally
            {
                  System.out.println("T1 ended...");
            }

      }


      /**
      * @param args
      */
      public static void main(String[] args)
      {
            // TODO Auto-generated method stub
            System.out.println("Main Started...");
            System.out.println("Main Thread Type="+Thread.currentThread().isDaemon());
            DeamonSample deamonSample=new DeamonSample();
            Thread t1=new Thread(deamonSample);
            t1.setDaemon(true);
            t1.start();
            System.out.println("T1 Type="+t1.isDaemon());
            System.out.println("Main Thread Type="+Thread.currentThread().isDaemon());
            System.out.println("Main ended...");
      }

}

Answer 1

默认情况下线程不是守护线程。如果您使用任何不是守护进程的线程到达主程序的末尾，那么该进程将继续运行。通过调用 setDaemon(true)，您可以告诉 JVM 您的线程不应在 main 结束时阻止关闭。