這是一道單詞查詢樹的問題,
這裡講的比較詳細
https://www.cnblogs.com/justinh/p/7716421.html

class Trie {
	class TrieNode {

	    // R links to node children
	    private TrieNode[] links;

	    private final int R = 26;

	    private boolean isEnd;

	    public TrieNode() {
	        links = new TrieNode[R];
	    }

	    public
 
 boolean containsKey(char ch) {
	        return links[ch -'a'] != null;
	    }
	    public TrieNode get(char ch) {
	        return links[ch -'a'];
	    }
	    public void put(char ch, TrieNode node) {
	        links[ch -'a'] = node;
	    }
	    public void setEnd() {
	        isEnd = true;
	    }
	    public
 
 boolean isEnd() {
	        return isEnd;
	    }
	}
	private TrieNode root;

    public Trie() {
        root = new TrieNode();
    }
 // Inserts a word into the trie.
    public void insert(String word) {
        TrieNode node = root;
        for (int i = 0; i < word.length(); i++) {
            char
 
 currentChar = word.charAt(i);
            if (!node.containsKey(currentChar)) {
                node.put(currentChar, new TrieNode());
            }
            node = node.get(currentChar);
        }
        node.setEnd();
    }
    private TrieNode searchPrefix(String word) {
        TrieNode node = root;
        for (int i = 0; i < word.length(); i++) {
           char curLetter = word.charAt(i);
           if (node.containsKey(curLetter)) {
               node = node.get(curLetter);
           } else {
               return null;
           }
        }
        return node;
    }

    // Returns if the word is in the trie.
    public boolean search(String word) {
       TrieNode node = searchPrefix(word);
       return node != null && node.isEnd();
    }
 // Returns if there is any word in the trie
    // that starts with the given prefix.
    public boolean startsWith(String prefix) {
        TrieNode node = searchPrefix(prefix);
        return node != null;
    }
}