code: protected void appendIdentityHashCode(StringBuilder buffer, Object object) {
          if (this.isUseIdentityHashCode() && object != null) {
              register(object);
              buffer.append('@');
              buffer.append(Integer.toHexString(System.identityHashCode(object)));
          }
      }
docs: <p>Append the {@link System#identityHashCode(Object)}.</p>
  
  @param buffer the <code>StringBuilder</code> to populate
  @param object the <code>Object</code> whose id to output