public static boolean isHex(String str){
  if (str == null || str.length() == 0)   return false;
  for (int i=str.length() - 1; i >= 0; i--) {
    char c=str.charAt(i);
    if (!(c >= '0' && c <= '9')) {
      c=Character.toLowerCase(c);
      if (!(c == 'a' || c == 'b' || c == 'c' || c == 'd' || c == 'e' || c == 'f'))       return false;
    }
  }
  return true;
}

public static boolean isHex ( String str ) { if ( str == null || str . length ( ) == 0 ) return false ; for ( int i = str . length ( ) - 1 ; i >= 0 ; i -- ) { char c = str . charAt ( i ) ; if ( ! ( c >= '0' && c <= '9' ) ) { c = Character . toLowerCase ( c ) ; if ( ! ( c == 'a' || c == 'b' || c == 'c' || c == 'd' || c == 'e' || c == 'f' ) ) return false ; } } return true ; }
tests if string value is hex value
