code: private static void addPrintable(StringBuffer retval, char ch) {
  		switch (ch) {
  		case '\b':
  			retval.append("\\b");
  			break;
  		case '\t':
  			retval.append("\\t");
  			break;
  		case '\n':
  			retval.append("\\n");
  			break;
  		case '\f':
  			retval.append("\\f");
  			break;
  		case '\r':
  			retval.append("\\r");
  			break;
  		case '\"':
  			retval.append("\\\"");
  			break;
  		case '\'':
  			retval.append("\\\'");
  			break;
  		case '\\':
  			retval.append("\\\\");
  			break;
  		default:
  			if (ch < 0x20 || ch > 0x7e) {
  				final String ss = "0000" + Integer.toString(ch, 16);
  				retval.append("\\u" + ss.substring(ss.length() - 4, ss.length()));
  			} else {
  				retval.append(ch);
  			}
  		}
  	}
docs: Adds the printable.
  
  @param retval the retval
  @param ch the ch