public void clearAdminUsers() {
        // Clear the admin list cache.
        if (adminList == null) {
            adminList = new ArrayList<>();
        }
        else {
            adminList.clear();
        }
        // Store empty list of admins with provider.
        provider.setAdmins(adminList);
    }
Clears the list of admin users.
xmppserver/src/main/java/org/jivesoftware/openfire/admin/AdminManager.java