Detect if a child exists

Question

I'm trying to check if a child exists in a location like this:

public static boolean checkIfNotebookExists(String notebookName) {
    if (notebooksRef.child(notebookName) == null)
        return false;
    else
        return true;
}

Whenever I call this function, I always get true even though the parameter that I include doesn't exist yet on the database.