public synchronized Collection<MonitoredTask> getTasks() {
    return Collections.unmodifiableCollection(this.tasks);
  }
Add a new task to the group, and before that might complete the last task in the group
@param description      the description of the new task
@param withCompleteLast whether to complete the last task in the group
@return the added new task
hbase-server/src/main/java/org/apache/hadoop/hbase/monitoring/TaskGroup.java