code: public static String unescapeJava(String str) {
          if (str == null) {
              return null;
          }
          try {
              Writer writer = new StringBuilderWriter(str.length());
              unescapeJava(writer, str);
              return writer.toString();
          } catch (IOException ioe) {
              // this should never ever happen while writing to a StringBuilderWriter
              throw new RuntimeException(ioe);
          }
      }
docs: Unescapes any Java literals found in the <code>String</code>.
  For example, it will turn a sequence of <code>'\'</code> and
  <code>'n'</code> into a newline character, unless the <code>'\'</code>
  is preceded by another <code>'\'</code>.
  
  @param str  the <code>String</code> to unescape, may be null
  @return a new unescaped <code>String</code>, <code>null</code> if null string input