* <p>
 * This class now uses the standard {@link java.util.Base64} implementation
 * instead of a custom implementation, providing better security and performance.
 * The API remains backward compatible with previous versions.
 * </p>
 *
 * @author higa
 */
public abstract class Base64Util {

    /**
     * Do not instantiate.
     */
    protected Base64Util() {
    }

    /**

     */
    @Size(max = 1000)
    public String notificationTo;

    /**
     * Enable or disable search suggestions based on search logs.
     * When enabled, suggestions are generated from previous searches.
     */
    @Size(max = 10)
    public String suggestSearchLog;

    /**
     * Enable or disable search suggestions based on document content.

                    deleteOldDocs();
                }
            }
        }

        /**
         * Deletes old documents from the search index.
         * This method removes documents that were indexed in previous
         * crawling sessions for the same data configuration, keeping
         * only the documents from the current session.
         *
         * <p>The deletion process:</p>
         * <ul>

    /**
     * Replaces the value of the entry with a new value.
     *
     * @param entry
     *            the entry
     * @param value
     *            the new value for the entry
     * @return the previous value of the entry
     */
    protected V swapValue(final Entry<K, V> entry, final V value) {
        final V old = entry.value;
        entry.value = value;
        return old;
    }

    /**

    protected String[] supportedLanguages;

    /** A list of shutdown hooks to be executed on system shutdown. */
    protected List<Runnable> shutdownHookList = new ArrayList<>();

    /** The previous state of the cluster. */
    protected AtomicInteger previousClusterState = new AtomicInteger(0);

    /** The version of the Fess application. */
    protected String version;

    /** The major version number. */