The ThreadGroup class in java

The ThreadGroup class manages groups of threads for Java applications. A ThreadGroup can contain any number of threads. The threads in a group are generally related in some way, such as who created them, what function they perform, or when they should be started and stopped.

ThreadGroups can contain not only threads but also other ThreadGroups. The top-most thread group in a Java application is the thread group named main. You can create threads and thread groups in the main group. You can also create threads and thread groups in subgroups of main. The result is a root-like hierarchy of threads and thread groups:

The ThreadGroup class has methods that can be categorized as follows:

• Collection Management Methods--Methods that manage the collection of threads and subgroups contained in the thread group.
• Methods That Operate on the Group--These methods set or get attributes of the ThreadGroup object.
• Methods That Operate on All Threads within a Group--This is a set of methods that perform some operation, such as start or resume, on all the threads and subgroups within the ThreadGroup.
• Access Restriction Methods--ThreadGroup and Thread allow the security manager to restrict access to threads based on group membership.