private ValueHolder getHolderByIntervalName(String aIntervalName){
		ValueHolder h = values.get(aIntervalName);
		if (h == null)
			throw new UnknownIntervalException(aIntervalName);
		return h;
	}
private ValueHolder getHolderByIntervalName ( String aIntervalName ) { ValueHolder h = values . get ( aIntervalName ) ; if ( h == null ) throw new UnknownIntervalException ( aIntervalName ) ; return h ; }
This method returns the ValueHolder that is stored for the given Interval name.

@param aIntervalName the name of the interval
@return the stored ValueHolder
@throws UnknownIntervalException if there is no ValueHolder stored for an Interval with the given name