question: private static void expand3DigitNumber ( String numberString , WordRelation wordRelation ) { if ( numberString . charAt ( 0 ) == '0' ) { expandNumberAt ( numberString , 1 , wordRelation ) ; } else { String hundredDigit = digit2num [ numberString . charAt ( 0 ) - '0' ] ; wordRelation . addWord ( hundredDigit ) ; wordRelation . addWord ( "hundred" ) ; expandNumberAt ( numberString , 1 , wordRelation ) ; } }
target:  Expands a three-digit string into a list of English words.