pre : c is an english letter , in upper or lower case concode_field_sep String _str concode_field_sep LetterInventory add concode_elem_sep int size concode_elem_sep LetterInventory subtract concode_elem_sep boolean equals concode_elem_sep boolean isEmpty concode_elem_sep String toString
int function ( char arg0 ) { if ( ! Character . isLetter ( arg0 ) ) throw new IllegalArgumentException ( ) ; int loc0 = 0 ; for ( int loc1 = 0 ; loc1 < _str . length ( ) ; loc1 ++ ) { if ( _str . charAt ( loc1 ) == arg0 ) loc0 ++ ; } return loc0 ; }