Thread Groups in Java

•If a program consists of large number of threads, we can divide them into groups and control each group as a whole.
•This can be achieved by using the predefined class in Java namely “ThreadGroup”.
•Every thread by default is assigned to a default group generally the “main” group.
•To create a new thread group, we must use the constructor of the “ThreadGroup” class. It is available in “java.lang” package.
•Following are the constructors in the “Threadgroup” class:
1) ThreadGroup(String Groupname)
2) ThreadGroup(ThreadGroup parent, String name)


•A thread must be assigned to a thread group, before calling the start() method of the thread. Once the start() method has been invoked, we cannot change the thread group.
•After creating a thread group, we can add threads to it by using the following constructors available in the “Thread” class:
1) Thread(ThreadGroup group, Runnable object)
2) Thread(ThreadGroup group, String name)
3) Thread(ThreadGroup group, Runnable object, String name)