Trie树的简单实现

import java.util.ArrayList;
import java.util.TreeMap;

import util.FileOperation;

public class Trie {
    private class Node{
        public boolean isWord;
        public TreeMap<Character,Node> next;

        public Node(boolean isWord) {
            this.isWord=isWord;
            next=new TreeMap<>();
        }
        public Node() {
            this(false);
        }
    }
    private Node root;
    private int size;
    public Trie() {
        root=new Node();
        size=0;
    }

    public int getSize() {
        return size;
    }
    public void add(String word) {

        Node cur=root;
        for(char c:word.toCharArray()) {
            if(cur.next.get(c)==null)
                  cur.next.put(c, new Node());
            cur=cur.next.get(c);
        }
        if(!cur.isWord) {
            cur.isWord=true;
            size++;
        }
    }

    public boolean find(String word) {
        Node cur=root;
        for(char c:word.toCharArray()) {
            if(cur.next.get(c)==null)
                  return false;
            cur=cur.next.get(c);
        }
        return cur.isWord;
    }

    public boolean isPrefix(String word) {
        Node cur=root;
        for(char c:word.toCharArray()) {
            if(cur.next.get(c)==null)
                  return false;
            cur=cur.next.get(c);
        }
        return true;
    }

    public boolean searchRegex(String word) {
        return match(root,word,0);
    }
    private boolean match(Node node,String word,int index) {
        if(index==word.length()) return node.isWord;
        else {
            char c=word.charAt(index);
            if(c!='.') {
                if(node.next.get(c)==null) return false;
                return match(node.next.get(c), word, index+1);
            }else {
                for(char w:node.next.keySet()) {
                    if(match(node.next.get(w), word, index+1)) {
                        return true;
                    }
                }
                return false;
            }
        }
    }
    public static void main(String[] args) {

        System.out.println("Pride and Prejudice");

        ArrayList<String> words = new ArrayList<>();
        if(FileOperation.readFile("pride-and-prejudice.txt", words)){

            long startTime = System.nanoTime();
            long endTime = System.nanoTime();
            // ---
            startTime = System.nanoTime();
            Trie trie = new Trie();
            for(String word: words)
                trie.add(word);
            for(String word: words)
                trie.find(word);
            endTime = System.nanoTime();

            double time = (endTime - startTime) / 1000000000.0;

            System.out.println("Total different words: " + trie.getSize());
            System.out.println("Trie: " + time + " s");
        }

    }
}