Trie using Array

TrieUsingArray

package dsa;

import java.util.ArrayList;
import java.util.List;

public class TrieUsingArray {
	
	TrieNode root;
	
	TrieUsingArray() {
		root = new TrieNode();
	}
	
	static class TrieNode {
		TrieNode[] children = new TrieNode[26];
		boolean isEndOfWord;
	}
	
	public void insert(String word) {
		TrieNode currentNode = root;

		for (int i=0;i<word.length();i++) {
			char c = word.charAt(i);
			int index = c - 'a';
			if (currentNode.children[index] == null) {
				currentNode.children[index] = new TrieNode();
			}
			
			currentNode = currentNode.children[index];
		}
		
		currentNode.isEndOfWord = true;
	}
	
	public List<String> suggest(String prefix) {
		List<String> suggestions = new ArrayList<>();
		TrieNode currentNode = root;
		
		for(int i=0;i<prefix.length();i++) {
			char c = prefix.charAt(i);
			int index = c - 'a';
			currentNode = currentNode.children[index];
			if (currentNode == null) {
				break;
			}	
		}
		
		if (currentNode != null) {
			collectAllWordsUnderNode(currentNode, prefix, suggestions);
		}
		
		return suggestions;
	}
	
	private void collectAllWordsUnderNode(TrieNode node, String prefix, List<String> words) {
		if(node.isEndOfWord) {
			words.add(prefix);
		}
		
		for(int i=0;i<node.children.length;i++) {
			if (node.children[i] != null) {
				collectAllWordsUnderNode(node.children[i], prefix + (char)('a' + i), words);
			}
		}
	}
	
	public void display() {
		internalDisplay(root, "");
	}
	
	public void internalDisplay(TrieNode node, String word) {
		if (node.isEndOfWord) {
			System.out.println(word);
		}
		
		for(int i=0;i<node.children.length;i++) {
			if (node.children[i] != null)
				internalDisplay(node.children[i], word + (char)('a' + i));
		}
	}

	public static void main(String[] args) {
		TrieUsingArray trie = new TrieUsingArray();
		trie.insert("cat");
		trie.insert("cam");
		
		trie.display();
		
		System.out.println(trie.suggest("c"));
	}

}