Use Iterator instead of looping. For example:
Iterator<Clientuser> iterator = EIQserver.OnlineusersList.iterator();
while (iterator.hasNext()) {
Clientuser next = iterator.next();
if(next.ID.equals(thsisUser.ID)) {
Omsg.setBody("@@!&$$$$@@@####$$$$");
sendMessage(Omsg);
iterator.remove();// remove the partner
}
}