Processes contain threads. Threads are lightweight processes that are handled by the JVM instead of by the operating system.
A2:
The sleep() method is declared to be static, which means that there is only one copy of this method and that it resides at the class level. As a result, you can call it with either a handle to an instance or the name of the class. The preferred approach is to call it with the name of the class.
A3:
The synchronize keyword signals that locks should be used to allow only one thread at the time to access a method.
A4:
The simple join() method will wait forever for another process to finish. The version that takes a parameter n will time out after n milliseconds and resume the thread's execution, with or without the other thread finishing.
