Question

Recently,I read “Java Network Programming”,in section 5.5,part 5.5.2.6 ,it has the following code:

public TimeSlicer(long milliseconds, int priority) {

    this.timeslice = milliseconds;

    this.setPriority(priority);

    // If this is the last thread left, it should not
    // stop the VM from exiting

    this.setDaemon(true);

}

just not quite understand the comments,what is the relationship of a daemon thread with the VM exiting?Thank you in advance.

Answer 1

The Java VM exits when there are no non-daemon threads left running. By marking a thread as a daemon thread using setDaemon(true), you are telling the VM that it is okay to exit even if this thread is still left running.

From the java.lang.Thread documentation:

Marks this thread as either a daemon thread or a user thread. The Java Virtual Machine exits when the only threads running are all daemon threads.