What is a ThreadGroup?
Created May 8, 2012
Brandon Rohlfs
A ThreadGroup is used to represent a group of Threads. A tree structure can be formed from ThreadsGroups containing other ThreadGroups. Threads can only access the ThreadGroup to which they belong. This means that access to a ThreadGroups parent or other ThreadGroup is not permitted. Once a ThreadGroup is created various information can be obtained such as the ThreadGroups name, how many threads are active, the maximum priority that can be contained within the group and a host of other information.
The ThreadGroup class provides two constructors.
ThreadGroup(String name) ThreadGroup(ThreadGroup parent, String name)
public class ThreadGroupTest{
public static void main(String[] args){
ThreadGroup squares = new ThreadGroup("Squares");
Thread t1 = new Thread(squares, new T(), "t1");
Thread t2 = new Thread(squares, new T(), "t2");
t1.start();
t2.start();
System.out.println("ThreadGroup name is: " + squares.getName());
System.out.println("There are currently " + squares.activeCount() + " threads running");
System.out.println("The maximum priority of a Thread that can be contained
within " + squares.getName() + " is " + squares.getMaxPriority());
System.out.println("There are currently " + squares.activeGroupCount() + " active groups");
System.out.println(squares.getName() + " parent is " + squares.getParent());
}
}
class T implements Runnable{
private int square;
public void run(){
for(int i = 1; i < 5; i++){
square = i * i;
System.out.println("Thread " + Thread.currentThread().getName() +
" has a priority of " + Thread.currentThread().getPriority() +
": " + square);
}
}
}