number of nodes in trie node

Here, I have created a class Trie and TrieNode, that implements Trie data structure in Java. I have a task to write a method called size() [return type int] to return the number of nodes in the Trie.

class Trie {

    private TrieNode root;

    /////////////////////
    // TrieNode class
    class TrieNode {
        public char c;
        public boolean isWord;
        public TrieNode[] children;

        public TrieNode(char c) {
            this.c = c;
            isWord = false;
            children = new TrieNode[26];
        }
    }

    public Trie() {
        root = new TrieNode('\0');
    }

    public boolean isPrefix(String word) {
        return getNode(word) != null;
    }

    public void insert(String word) {
        TrieNode curr = root;
        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if (curr.children[c - 'A'] == null)
                curr.children[c - 'A'] = new TrieNode(c);
            curr = curr.children[c - 'A'];
        }
        curr.isWord = true;
    }

    // Helper
    private TrieNode getNode(String word) {
        TrieNode curr = root;
        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            if (curr.children[c - 'A'] == null)
                return null;
            curr = curr.children[c - 'A'];
        }
        return curr;
    }

I have been trying to get the number of nodes in the Trie, and what I was thinking about is:

    public int size() {
        return size(root);
    }

    private int size(TrieNode root) {

        for (int i = 0; i < root.children.length; i++) {
            if (root.children[i] != null) {
                if (root.isWord)
                return 1;
                else
                    return 1 + size(root.children[i]);
            }
        }
        return 0;
    }

But it is not right. Any ideas?

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