Thread extends  java.lang. A thread is a thread of executing in a program. The Java Virtual Machine allows an application to have multiple threads of executing running concurrently.
Every thread has a priority.
Threads with higher priority are executed in preference to threads with lower priority. There are two ways to create a new thread of execution One is to declare a class to be a subclass of Thread. This subclass should override the run method of class Thread. An instance of the subclass can then be allocated and started. That class then implements the run method.