Daemon threads in Java

Threads that work in the background to support the runtime environment are called daemon threads. For example, the clock handler thread, the idle thread, the screen updater thread, and the garbage collector thread are all daemon threads. The virtual machine exits whenever all non-daemon threads have completed.

public final void setDaemon(boolean isDaemon)
public final boolean isDaemon()

By default a thread you create is not a daemon thread. All the user applications are generally started off as non-daemon threads. However you can use the setDaemon(true) method to turn it into one.