Hackerrank contacts problem

solution.java

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static class Node {
        public Character value;
        private HashMap<Character, Node> children = new HashMap<Character, Node>();
        public boolean isCompleteWord;
        //To speed up the countCompletedWords
        public int numWords = 0;
        
        Node(Character value, boolean isCompleteWord) {
            this.value = value;
            this.isCompleteWord = isCompleteWord;
        }
        
        public Node putChild(Character letter, boolean isCompleteWord) {
            Node node = new Node(letter, isCompleteWord);
            children.put(letter, node);
            return node;
        }
        
        public Node getChild(Character letter) {
            return children.get(letter);
        }
        
        /*
        too slow...
        public int countCompletedWords() {
            int total = 0;
            for(Map.Entry<Character, Node> entry : children.entrySet()) {
                total += entry.getValue().countCompletedWords();
            }
            if(this.isCompleteWord) {
                total++;
            }
            return total;
        }
        */
        
        public int countCompletedWords() {
            return numWords;
        }
        
        public String toString() {
            String result = this.value + "("+this.numWords+"):{\n";
            for(Map.Entry<Character, Node> entry : children.entrySet()) {
                result += "\t" + entry.getValue().toString();
            }
            result += "}\n";
            return result;
        }
    }
    
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        Node root = new Node('*', false);
        
        for(int a0 = 0; a0 < n; a0++){
            String op = in.next();
            String contact = in.next();
            if(op.equals("add")) {
                add(root, contact);
            }
            if(op.equals("find")) {
                //System.out.println(root.toString());
                System.out.println(find(root, contact));
            }
        }
        
    }
    
    public static void add(Node root, String word) {
        Node currentNode = root;
        for(int i = 0; i < word.length(); i++) {
            Character letter = word.charAt(i);
            Node existingLetterNode = currentNode.getChild(letter);
            if(existingLetterNode != null) {
                currentNode = existingLetterNode;
                currentNode.numWords++;
                continue;
            }
            currentNode = currentNode.putChild(letter, false);
            currentNode.numWords++;
        }
        currentNode.putChild('*', true);
    }
    
    public static int find(Node root, String word) {
        Node currentNode = root;
        for(int i = 0; i < word.length(); i++) {
            Character letter = word.charAt(i);
            currentNode = currentNode.getChild(letter);
            if(currentNode == null) {
                break;
            }
        }
        if(currentNode == null) {
            return 0;
        }
        
        return currentNode.countCompletedWords();
    }
}