@Override
    public boolean hasNext() {
      return !nextElements.isEmpty();
    }

    @Override
    public boolean hasPrevious() {
      return !previousElements.isEmpty();
    }

    @Override
    public E next() {
      return transferElement(nextElements, previousElements);
    }

    @Override
    public int nextIndex() {
      return previousElements.size();
    }

    @Override

     *
     * @return the default filter chain
     */
    protected FilterChain createDefaultFilterChain() {
        return query -> {
            try {
                return createQueryParser().parse(query);
            } catch (final ParseException e) {
                throw new QueryParseException(e);
            }
        };
    }

    /**

     *
     * @return the unique identifier of type IDTYPE.
     */
    IDTYPE getId();

    /**
     * Sets the unique identifier for the URL queue.
     *
     * @param id the unique identifier to set
     */
    void setId(IDTYPE id);

    /**
     * Retrieves the session ID associated with this URL queue.
     *
     * @return the session ID as a String.
     */

    protected T doForward(String value) {
      return Enum.valueOf(enumClass, value);
    }

    @Override
    protected String doBackward(T enumValue) {
      return enumValue.name();
    }

    @Override
    public boolean equals(@Nullable Object obj) {
      if (obj instanceof StringConverter) {
        StringConverter<?> that = (StringConverter<?>) obj;
        return this.enumClass.equals(that.enumClass);
      }

     *
     * @return a {@link SchemaFactory} for W3C XML Schema
     */
    public static SchemaFactory newW3cXmlSchemaFactory() {
        return newW3cXmlSchemaFactory(false);
    }

    /**
     * Creates a {@link SchemaFactory} for W3C XML Schema.
     *
     * @param external
     *            If {@code true}, external access is allowed.
     * @return a {@link SchemaFactory} for W3C XML Schema
     */

     *
     * @return the server address
     */
    public String getServerAddress() {
        return serverAddress;
    }

    /**
     * Sets the server address.
     *
     * @param serverAddress the server address
     */
    public void setServerAddress(String serverAddress) {
        this.serverAddress = serverAddress;
    }

    /**
     * Gets the registration flags.
     *
     * @return the flags

    }

    public Severity getSeverity() {
        return severity;
    }

    public Version getVersion() {
        return version;
    }

    public Exception getException() {
        return exception;
    }

    public ModelProblemCollectorRequest setException(Exception exception) {
        this.exception = exception;
        return this;
    }

    public String getMessage() {

 */
@Experimental
public interface Event {

    /**
     * Gets the type of the event.
     *
     * @return the type of the event, never {@code null}
     */
    @Nonnull
    EventType getType();

    /**
     * Gets the session from which this event originates.
     *
     * @return the current session, never {@code null}
     */
    @Nonnull
    Session getSession();

    /**

            return 0;
        }
        if (i1 == -1) {
            // second one is known, so it comes first
            return 1;
        }
        if (i2 == -1) {
            // first one is known, so it comes first
            return -1;
        }
        int rv = Integer.compare(i1, i2);
        if (rv != 0) {
            return rv;
        }

            return DoubleConversionUtil.toDouble(o);
        } else if (type == Long.class) {
            return LongConversionUtil.toLong(o);
        } else if (type == Float.class) {
            return FloatConversionUtil.toFloat(o);
        } else if (type == Short.class) {
            return ShortConversionUtil.toShort(o);
        } else if (type == BigInteger.class) {
            return BigIntegerConversionUtil.toBigInteger(o);