# 1797. Design Authentication Manager
###### tags: `Leetcode` `Medium` `HashMap`
Link: https://leetcode.com/problems/design-authentication-manager/
## 思路
注意在countUnexpiredTokens function里面由于想要清除掉expired tokens所以用了removeIf function 需要记住用法
因为如果换成

for(int num:map.keySet()){
    if(map.get(num)<=currentTime) map.remove(num)
}

会报错，因为不能在遍历的key set的时候删掉key
## Code

class AuthenticationManager {
    int time;
    Map<String, Integer> map;
    public AuthenticationManager(int timeToLive) {
        time = timeToLive;
        map = new HashMap<>();
    }
    
    public void generate(String tokenId, int currentTime) {
        map.put(tokenId, currentTime+time);
    }
    
    public void renew(String tokenId, int currentTime) {
        if(map.containsKey(tokenId) && map.get(tokenId)>currentTime) map.put(tokenId, currentTime+time);
    }
    
    public int countUnexpiredTokens(int currentTime) {
        map.entrySet().removeIf(e -> e.getValue() <= currentTime);
        return map.size();
    }
}