守护线程是在后台执行一些任务的线程，比如处理请求或应用程序中可能存在的各种chronjob。

当你的程序只剩下守护线程时，它将退出。这是因为这些线程通常与普通线程一起工作，并提供事件的后台处理。

你可以使用setDaemon方法指定一个线程是守护线程，它们通常不会退出，也不会被中断。当应用程序停止时，它们就会停止。

Daemon thread is like daemon process which is responsible for managing resources,a daemon thread is created by the Java VM to serve the user threads. example updating system for unix,unix is daemon process. child of daemon thread is always daemon thread,so by default daemon is false.you can check thread as daemon or user by using "isDaemon()" method. so daemon thread or daemon process are basically responsible for managing resources. for example when you starting jvm there is garbage collector running that is daemon thread whose priority is 1 that is lowest,which is managing memory. jvm is alive as long as user thread is alive,u can not kill daemon thread.jvm is responsible to kill daemon threads.

我想澄清一个误解:

Assume that if daemon thread (say B) is created within user thread (say A); then ending of this user thread/parent thread (A) will not end the daemon thread/child thread (B) it has created; provided user thread is the only one currently running. So there is no parent-child relationship on thread ending. All daemon threads (irrespective of where it is created) will end once there is no single live user thread and that causes JVM to terminate. Even this is true for both (parent/child) are daemon threads. If a child thread created from a daemon thread then that is also a daemon thread. This won't need any explicit daemon thread flag setting. Similarly if a child thread created from a user thread then that is also a user thread, if you want to change it, then explicit daemon flag setting is needed before start of that child thread.

Java守护线程

(守护进程)

Java使用用户线程和守护进程线程概念。

JVM流

1. If there are no `user treads` JVM starts terminating the program
2. JVM terminates all `daemon threads` automatically without waiting when they are done
3. JVM is shutdown

正如你所看到的，守护线程是用户线程的服务线程。

守护线程是低优先级线程。 线程从父线程继承它的属性。要从外部设置它，你可以在启动它之前使用setDaemon()方法或通过isDaemon()检查它

守护线程是在后台执行一些任务的线程，比如处理请求或应用程序中可能存在的各种chronjob。

当你的程序只剩下守护线程时，它将退出。这是因为这些线程通常与普通线程一起工作，并提供事件的后台处理。

你可以使用setDaemon方法指定一个线程是守护线程，它们通常不会退出，也不会被中断。当应用程序停止时，它们就会停止。

守护线程和用户线程。通常程序员创建的所有线程都是用户线程(除非你指定它为守护线程或者你的父线程是守护线程)。用户线程通常用于运行我们的程序代码。除非所有用户线程都终止，否则JVM不会终止。