Returning from async thread without making server wait?

I'm having some trouble getting data from an async thread without returning null. This is the sort of idea i'm going for, obviously relList will always return null as the function continues to the end as soon as BukkitRunnable is encountered.

Code:

public static Map<Integer, Map<Integer, String>> getList(){
        Map<Integer, Map<Integer, String>> relList = new HashMap<Integer, Map<Integer, String>>();
        Map<Integer, String> relInfo = new HashMap<Integer, String>();
        BukkitRunnable l = new BukkitRunnable(){
            @Override
            public void run(){
                Statement statement = null;
                ResultSet result = null;
                try{
                    statement = connection.createStatement();
                    result = statement.executeQuery("SELECT `key`, `name`, `description` FROM test.religions");
                    while(result.next()){
                        relInfo.put(1, result.getString(2));
                        relInfo.put(2, result.getString(3));
                        relList.put(result.getInt(1), relInfo);
                    }
                }catch(SQLException e){
                    e.printStackTrace();
                }
            }
        };
        l.runTaskAsynchronously(plugin);
        return relList;

I need to call this method from another thread so I can manipulate the data. Is there a way I can return relList without making the server wait?

 

To be sure I'm correct, you're telling me I should call getList() and then return to the original class with another method call to the manipulation underneath it? So something like:

Code:

onCommand(){
    if(args.length == 0){
        getList();
    }
}

returnList(){
    //data manipulation here
}