ThreadGroup

        # ThreadGroup < Object

(from ruby core)
---
ThreadGroup provides a means of keeping track of a number of threads as
a group.

A given Thread object can only belong to one ThreadGroup at a time;
adding a thread to a new group will remove it from any previous group.

Newly created threads belong to the same group as the thread from which
they were created.
---
# Constants:

Default
:   The default ThreadGroup created when Ruby starts; all Threads belong
    to it by default.


# Instance methods:

    add
    enclose
    enclosed?
    list