Example of implementing a trie. Includes inserting and searching the trie (deletion not included.)

Trie.java

import java.io.*;

public class Trie
{
	private TrieNode root;

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

	public void insert( String s )
	{
		/* Begin at root */
		TrieNode current = root;

		if( s.length() == 0 )
		current.marker = true;

		/* Add the word */
		for( int i = 0; i < s.length(); i++ ) {

			/* See if the letter is already in the trie */
			TrieNode child = current.subNode( s.charAt(i) );

			if( child != null )
			/* If the letter was in the trie, switch to it and continue */
			current = child;
			else {
				/* If the letter wasn't in the trie, add it */
				current.child.add( new TrieNode( s.charAt(i) ) );

				/* Switch to the new node */
				current = current.subNode( s.charAt(i) );
			}

			if( i == s.length() - 1 )
			current.marker = true;
		}
	}

	public boolean search( String s )
	{
		/* Begin at the root */
		TrieNode current = root;

		while( current != null ) {
			for( int i = 0; i < s.length(); i++ ) {
				if( current.subNode( s.charAt(i) ) == null ) {
					return false;
				} else {
					current = current.subNode( s.charAt( i ) );
				}
			}

			if( current.marker = true )
			return true;
			else
			return false;
		}

		return false;
	}

	public void run() throws IOException
	{
		String s = " ";
		BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );
		while( s.length() > 0 && s.charAt(0) != 'q' ) {
			System.out.println( "Please enter a new word to be added to the trie:" );
			s = br.readLine();

			if( s.charAt(0) != 'q') {
				insert( s );	
			}
		}

		s = " ";
		while( s.length() > 0 && s.charAt(0) != 'q' ) {
			System.out.println( "Please enter a new word to search for in the trie:" );
			s = br.readLine();

			if( s.charAt(0) != 'q') {
				if( search( s ) ) {
					System.out.println( "Found " + s );
				} else {
					System.out.println( "Couldn't find " + s );
				}
			}
		}
	}

	public static void main( String[] args ) throws IOException
	{
		Trie t = new Trie();
		t.run();
	}
}

TrieNode.java

import java.util.Collection;
import java.util.LinkedList;

public class TrieNode
{
	char content;
	boolean marker;
	Collection<TrieNode> child;

	public TrieNode( char c )
	{
		this.child = new LinkedList<TrieNode>();
		this.marker = false;
		this.content = c;
	}

	public TrieNode subNode( char c )
	{
		if( child != null ) {
			for( TrieNode eachChild : child ) {
				if( eachChild.content == c ) {
					return eachChild;
				}
			}
		}

		return null;
	}
}