1797. 设计一个验证系统

class AuthenticationManager {
    int timeToLive; 
    Map<String, Integer> map;

    public AuthenticationManager(int timeToLive) {
        this.timeToLive = timeToLive;
        this.map = new HashMap<String, Integer>();
    }
    
    public void generate(String tokenId, int currentTime) {
        map.put(tokenId, timeToLive + currentTime);
    }
    
    public void renew(String tokenId, int currentTime) {
        if(map.getOrDefault(tokenId, 0) > currentTime) {
            map.put(tokenId, timeToLive + currentTime);
        }
    }
    
    public int countUnexpiredTokens(int currentTime) {
        int count = 0;
        for (int time : map.values()) {
            if (time > currentTime) {
                count++;
            }
        }
        return count;
    }
}