}
        }

        // Clean up expired weak references
        cleanupExpiredReferences();

        // Release all leases
        releaseAll();

        // Clear file cache
        fileCache.clear();
    }

    /**
     * Clean up expired weak references from the file cache
     */
    private void cleanupExpiredReferences() {
        try {

     * @return the generated key
     * @throws IOException if an I/O error occurs
     */
    protected abstract long makeKey(Request request) throws IOException;

    /**
     * Peek at the next key without removing it from the input stream
     *
     * @return the next key or null if none available
     * @throws IOException if an I/O error occurs
     */