trie.java

public class Trie {

    static final int ALPHABET_SIZE = 26;

    static class TrieNode
    {
        TrieNode[] children = new TrieNode[ALPHABET_SIZE];

        boolean isEndOfWord;
         
        TrieNode(){
            isEndOfWord = false;
            for (int i = 0; i < ALPHABET_SIZE; i++)
                children[i] = null;
        }
    };
      
    static TrieNode root; 

    static void insert(String key)
    {
        int level;
        int length = key.length();
        int index;
      
        TrieNode pCrawl = root;
      
        for (level = 0; level < length; level++)
        {
            index = key.charAt(level) - 'a';
            if (pCrawl.children[index] == null)
                pCrawl.children[index] = new TrieNode();
      
            pCrawl = pCrawl.children[index];
        }

        pCrawl.isEndOfWord = true;
    }

    static boolean search(String key)
    {
        int level;
        int length = key.length();
        int index;
        TrieNode pCrawl = root;
      
        for (level = 0; level < length; level++)
        {
            index = key.charAt(level) - 'a';
      
            if (pCrawl.children[index] == null)
                return false;
      
            pCrawl = pCrawl.children[index];
        }
      
        return (pCrawl != null && pCrawl.isEndOfWord);
    }
}