*       Stream.map}).
 *   <li><b>Do not</b> call {@link #doForward} or {@link #doBackward} directly; these exist only to
 *       be overridden.
 * </ul>
 *
 * <h3>Example</h3>
 *
 * <pre>
 *   return new Converter&lt;Integer, String&gt;() {
 *     protected String doForward(Integer i) {
 *       return Integer.toHexString(i);
 *     }
 *
 *     protected Integer doBackward(String s) {
 *       return parseUnsignedInt(s, 16);

 *       Stream.map}).
 *   <li><b>Do not</b> call {@link #doForward} or {@link #doBackward} directly; these exist only to
 *       be overridden.
 * </ul>
 *
 * <h3>Example</h3>
 *
 * <pre>
 *   return new Converter&lt;Integer, String&gt;() {
 *     protected String doForward(Integer i) {
 *       return Integer.toHexString(i);
 *     }
 *
 *     protected Integer doBackward(String s) {
 *       return parseUnsignedInt(s, 16);