question: public static void expandLetters ( String letters , WordRelation wordRelation , Item tokenItem ) { letters = letters . toLowerCase ( ) ; char c ; for ( int i = 0 ; i < letters . length ( ) ; i ++ ) { c = letters . charAt ( i ) ; if ( isDigit ( c ) ) { wordRelation . addWord ( tokenItem , digit2num [ c - '0' ] ) ; } else if ( letters . equals ( "a" ) ) { wordRelation . addWord ( tokenItem , "_a" ) ; } else { wordRelation . addWord ( tokenItem , String . valueOf ( c ) ) ; } } }
target:  Expands the given string of letters as a list of single char symbols.