Daemon and user threads

1. Basic knowledge of ：

Threads are divided into user threads and guard threads
The virtual machine must make sure that the user thread is finished ( That is, the execution of the user thread ends , Virtual machine will end )
The virtual machine doesn't have to wait for the daemons to finish executing ( That is, the daemon thread and the virtual machine exist or die together )
Common daemon threads such as , Record the operation log in the background , Monitor memory , Garbage collection waiting …

2. Example

/** Daemons and user threads */
public class TestDaemon {
    
    
    public static void main(String[] args) {
    
        God god = new God();
        Person p = new Person();

        Thread daemon = new Thread(god);
        daemon.setDaemon(true); //  Set to daemons , Live or die with the virtual machine , The default is false, That is, the user thread is assumed by default 
        daemon.start();

        Thread common = new Thread(p);
        common.start();
    }

}

class God implements Runnable{
    
    @Override
    public void run() {
    
        while (true) {
    
            System.out.println(" God is watching over you ....");
        }
    }
}

class Person implements Runnable{
    
    @Override
    public void run() {
    
        for (int i = 1;i<35000;i++){
    
            System.out.println(" Live happily every day ....");
        }
        System.out.println("===========Goodbye world...");
    }
}

Execution results ：
The user thread and the daemon thread execute together

End of user thread execution , Daemon thread continues execution

Execute until the virtual machine stops .