Method loadButtonClass

/**
 * Load the button class including the deprecated ones.
 *
 * @param   string  $type  Button Type (normalized)
 *
 * @return  string|null
 *
 * @since   4.0.0
 */
private function loadButtonClass(string $type)
{
    $buttonClasses = [
        'Joomla\\CMS\\Toolbar\\Button\\' . $type . 'Button',
        // @deprecated 5.0
        'JToolbarButton' . $type,
    ];
    foreach ($buttonClasses as $buttonClass) {
        if (!class_exists($buttonClass)) {
            continue;
        }
        return $buttonClass;
    }
    return null;
}