Main thread and daemon thread

As long as there are threads running, the Java process will not end.
For daemon threads, as long as other non-daemon threads have finished running, even if the code of the daemon thread has not finished executing,
It will force the end of setDaemon(true) and set it as a daemon thread.
The garbage collector is a daemon thread
The Acceptor and Poller threads in Tomcat are both daemon threads