code: public static char[] getUpperCaseCharset(final int upto) {
          final int uptoPlusOne = upto + 1;
          final char[] characters = CHACHED_UPPER_CASE_CHARSETS.get(uptoPlusOne);
          if (characters != null) {
              return characters;
          }
          final char[] charset = new char[uptoPlusOne];
          char index = 0;
          while (index < uptoPlusOne) {
              charset[index] = Character.toUpperCase(index);
              index++;
          }
          final char[] previous = CHACHED_UPPER_CASE_CHARSETS
                  .putIfAbsent(uptoPlusOne, charset);
          if (previous != null) {
              return previous;
          }
          return charset;
      }
docs: gets the char array of upper case chars from 0 to the given {@code upto}
  value.
  
  @param upto
  @return
  @since 1.0.0
  @author WFF