[Android] thread, join

join的解釋如下：

final void	join() Blocks the current Thread (Thread.currentThread()) until the receiver finishes its execution and dies.
final void	join(long millis, int nanos) Blocks the current Thread (Thread.currentThread()) until the receiver finishes its execution and dies or the specified timeout expires, whatever happens first.
final void	join(long millis) Blocks the current Thread (Thread.currentThread()) until the receiver finishes its execution and dies or the specified timeout expires, whatever happens first.

來源資料：http://developer.android.com/reference/java/lang/Thread.html