code: static public char getHighChar(String encoding)
      {
          final char highCodePoint;
          EncodingInfo ei;
  
          String normalizedEncoding = toUpperCaseFast(encoding);
          ei = (EncodingInfo) _encodingTableKeyJava.get(normalizedEncoding);
          if (ei == null)
              ei = (EncodingInfo) _encodingTableKeyMime.get(normalizedEncoding);
          if (ei != null)
              highCodePoint =  ei.getHighChar();
          else
              highCodePoint = 0;
          return highCodePoint;
      }
docs: Characters with values at or below the high code point are
  in the encoding. Code point values above this one may or may
  not be in the encoding, but lower ones certainly are.
  <p>
  This is for performance.
  
  @param encoding The encoding
  @return The code point for which characters at or below this code point
  are in the encoding. Characters with higher code point may or may not be
  in the encoding. A value of zero is returned if the high code point is unknown.
  <p>
  This method is not a public API.
  @xsl.usage internal