面试常问：为什么敏感词过滤不用暴力匹配？

com.xxx.sensitive
├── SensitiveFilter.java       # 核心过滤入口
├── TrieNode.java              # 字典树节点
├── SensitiveWordConfig.java   # 敏感词配置/加载
├── SensitiveCache.java        # 缓存（本地/Redis）
└── SensitiveUtil.java         # 工具类：替换、特殊字符清洗

public class TrieNode {
    // 子节点 key:字符 value:节点
    private Map<Character, TrieNode> children;
    // 是否是词的结尾
    private boolean isEnd;

    public TrieNode() {
        this.children = new HashMap<>();
        this.isEnd = false;
    }
    // getter/setter
}

// 批量插入敏感词
public void addSensitiveWord(String word) {
    TrieNode node = root;
    for (char c : word.toCharArray()) {
        if (!node.getChildren().containsKey(c)) {
            node.getChildren().put(c, new TrieNode());
        }
        node = node.getChildren().get(c);
    }
    node.setEnd(true);
}

public String filter(String text) {
    if (text == null || text.isEmpty()) {
        return text;
    }
    StringBuilder result = new StringBuilder();
    int length = text.length();
    int i = 0;

    while (i < length) {
        TrieNode node = root;
        int j = i;
        boolean hit = false;
        // 沿着 Trie 树往下走
        while (j < length && node.getChildren().containsKey(text.charAt(j))) {
            node = node.getChildren().get(text.charAt(j));
            if (node.isEnd()) {
                hit = true;
                break;
            }
            j++;
        }
        if (hit) {
            // 命中敏感词，替换为 ***
            result.append("***");
            i = j + 1;
        } else {
            result.append(text.charAt(i));
            i++;
        }
    }
    return result.toString();
}

for (String word : sensitiveList) {
    if (text.contains(word)) {
        return true;
    }
}