How to write a recursive function to find number of nodes in a Trie?

Question

I am trying to create a size() function to return the number of nodes in my Trie but I am not sure what I need to change in TrieNode to make this possible. I create a Trie from a file with words in it and I would like it to return the number of nodes. So for a file with: cat car dog pick pickle I would like it to print trie size: 14 nodes.

class TrieNode {

    public final Map<Character, TrieNode> children = new HashMap<>();

    private boolean endOfWord;

    static final int ALPHABET_SIZE = 26;

    public Map<Character, TrieNode> getChildren() {
        return children;
    }
    boolean isEndOfWord() {
        return endOfWord;
    }

    void setEndOfWord(boolean endOfWord) {
        this.endOfWord = endOfWord;
    }

        int size(TrieNode node) {
            if(node == null)
                return 0;

            int total = 1;

            for(TrieNode child : node.children)
                total += size(child);

            return total;
        }

    public static void main(String[] args) throws IOException {
        Trie myTrie = new Trie();
        try {
            BufferedReader reader = new BufferedReader(new FileReader("test.txt"));
            String line;
            while ((line = reader.readLine()) != null)
                myTrie.insert(line);
        } catch (Exception e) {
            e.printStackTrace();
        }

        System.out.println("Trie Size: " + myTrie.size() + " nodes");