字典树||前缀树Java

class Trie 
{
    Map child = new HashMap<>();
    boolean isWord;

    
    public Trie() 
    {
        isWord = false;
    }
    
    
    public void insert(String word) 
    {
        Trie root = this;
        for (int i = 0; i < word.length(); i ++)
        {
            char c = word.charAt(i);
            if (root.child.containsKey(c) == false)
                root.child.put(c, new Trie());
            root = root.child.get(c);
        }
        root.isWord = true;
    }
    
    
    public boolean search(String word) 
    {
        Trie root = this;
        for (int i = 0; i < word.length(); i ++)
        {
            char c = word.charAt(i);
            if (root.child.containsKey(c) == false)
                return false;
            root = root.child.get(c);
        }
        return root.isWord == true;
    }
    
    
    public boolean startsWith(String prefix) 
    {
        Trie root = this;
        for (int i = 0; i < prefix.length(); i ++)
        {
            char c = prefix.charAt(i);
            if (root.child.containsKey(c) == false)
                return false;
            root = root.child.get(c);
        }
        return true;
    }
}