004 Daemon thread

I. Overview

　　A daemon thread is a special kind of thread whose particularity lies in:

　　　　[1] Depends on other non-daemon threads. Once there are no other types of threads running in the whole program, the daemon thread is automatically terminated.

　　　　[2] The priority level of operation is low, and some system-level auxiliary behaviors can be performed.

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2. Create a daemon thread.

　　In fact, creating a daemon thread is no different from a general thread, except that the thread needs to be set as a daemon thread before the thread starts.

　　example:　　　　

Thread thread = new Thread() {
            @Override
            public void run() {
                for(;;)
                    System.out.println(" I am is a daemon Thread ...");
            }
        };
        thread.setDaemon(true);
        thread.start();
        Thread.sleep(3000);
        System.out.println("end ....");

　　To create a daemon thread, you only need to pay attention to setting a daemon property.

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3. Operation results

　　We run the above code and find that the daemon thread automatically terminates itself after 3 seconds.

　　This is a feature of daemon threads. When there is no non-daemon thread running in the runtime environment, the daemon thread automatically terminates itself.