/** The key of the message: {item} may not be empty. */
    public static final String CONSTRAINTS_NotEmpty_MESSAGE = "{constraints.NotEmpty.message}";

    /** The key of the message: script expression "{script}" didn't evaluate to true. */
    public static final String CONSTRAINTS_ParametersScriptAssert_MESSAGE = "{constraints.ParametersScriptAssert.message}";

    /** The key of the message: {item} must be between {min} and {max}. */

    }

    /**
     * Adds the specified element to this set if it is not already present.
     *
     * @param o
     *            element to be added to this set.
     * @return true if the set did not already contain the specified
     *         element.
     */
    @Override
    public boolean add(final E o) {
        return map.put(o, PRESENT) == null;
    }

    /**

    public static final String LABELS_next_page = "{labels.next_page}";

    /** The key of the message: Your search - <b>{0}</b> - did not match any documents. */
    public static final String LABELS_did_not_match = "{labels.did_not_match}";

    /** The key of the message: Fess */
    public static final String LABELS_search_title = "{labels.search_title}";