public ArrayList<String> getUsersInGroup(int groupID){
        ArrayList<GroupMembership> allGroupMemberships = groupMemberships().getGroupMemberships();
        ArrayList<String> usersInGroup = new ArrayList<>();

        if(groupID == -1){
            usersInGroup = new ArrayList<>(users().getAllUsers());

            for(GroupMembership groupMembership : allGroupMemberships){
                usersInGroup.remove(groupMembership.getUsername());
            }
        }else{
            for(GroupMembership groupMembership : groupMemberships().getGroupMembershipsByGroupID(groupID)){
                if(groupMembership.getGroupID() == groupID) usersInGroup.add(groupMembership.getUsername());
            }
        }

        return usersInGroup;
    }