code: public boolean isUserAssociatedToGroup(String user, String group)
  	{
  		if (!isUserExist(user))
  		{
  			throw new SystemException(String.format("User '%s' does not exist.", user));
  		}
  
  		if (!isGroupExist(group))
  		{
  			throw new SystemException(String.format("Group '%s' does not exist.", group));
  		}
  
  		List<String> userGroups = allAssociations.get(user);
  
  		return userGroups != null && userGroups.contains(group);
  	}
docs: <p>isUserAssociatedToGroup.</p>
  
  @param user a {@link java.lang.String} object.
  @param group a {@link java.lang.String} object.
  @return a boolean.