code: public boolean equalsIgnoreCase(CharSequence x) {
          if (x == this) return true;
          if (null == x || size() != x.length()) return false;
          if (isEmpty() && x.length() == 0) return true;
          return regionMatches(true, 0, x, 0, size());
      }
docs: Wrapper of {@link String#equalsIgnoreCase(String)}
  
  @param x the char sequence to be compared
  @return {@code true} if the argument is not {@code null} and it
  represents an equivalent {@code String} ignoring case; {@code
  false} otherwise