Determining When a Thread Ends
It is often useful to know when a thread has ended. For example, in the preceding examples, for the sake of illustration it was helpful to keep the main thread alive until the other threads ended. In those examples, this was accomplished by having the main thread sleep longer than the child threads that it spawned. This is, of course, hardly a satisfactory or generalizable solution!
Fortunately, Thread provides two means by which you can determine if a thread has ended. First, you can call isAlive( ) on the thread. Its general form is shown here:
final boolean isAlive( )
The isAlive( ) method returns true if the thread upon which it is called is still running. It returns false otherwise. To try isAlive( ), substitute ...