question: public static < T > BigDecimal sumOfBigDecimal ( Iterable < T > iterable , Function < ? super T , BigDecimal > function ) { if ( iterable instanceof List ) { return ListIterate . sumOfBigDecimal ( ( List < T > ) iterable , function ) ; } if ( iterable != null ) { return IterableIterate . sumOfBigDecimal ( iterable , function ) ; } throw new IllegalArgumentException ( "Cannot perform an sumOfBigDecimal on null" ) ; }
target:  Returns the BigDecimal sum of the result of applying the function to each element of the iterable.