code: public static String filterEncode(String value) {
  
          if (value == null)
              return null;
  
          // make buffer roomy
          StringBuilder encodedValue = new StringBuilder(value.length() * 2);
  
          int length = value.length();
  
          for (int i = 0; i < length; i++) {
  
              char c = value.charAt(i);
  
              if (c < FILTER_ESCAPE_TABLE.length) {
                  encodedValue.append(FILTER_ESCAPE_TABLE[c]);
              } else {
                  // default: add the char
                  encodedValue.append(c);
              }
          }
  
          return encodedValue.toString();
      }
docs: Escape a value for use in a filter.
  
  @param value
  the value to escape.
  @return a properly escaped representation of the supplied value.