import org.apache.activeblaze.group.*;

...
BlazeGroupChannelFactory factory = new BlazeGroupChannelFactory();

BlazeGroupChannel channel = factory.createGroupChannel("My Channel");
//join a group
channel.addToGroup("test");
channel.start();

//listen for other members

channel.addMemberChangedListener(new MemberChangedListener(){

     public void memberStarted(Member member) {
         System.out.println("Member started");
     }

     public void memberStopped(Member member) {
         System.out.println("Member stopped");
     }
            
 });