Easy answer in 1 loop
Complexity
Time complexity: O(n)

Space complexity: O(1)
Code

<!-- Describe your approach to solving the problem. -->

# Complexity
- Time complexity: ***O(n)***
<!-- Add your time complexity here, e.g. $$O(n)$$ -->

- Space complexity: ***O(1)***
<!-- Add your space complexity here, e.g. $$O(n)$$ -->

# Code
```java []
class Solution {
    public boolean isAcronym(List<String> words, String s) {
        if(words.size() != s.length()){
            return false;
        }

        for(int i=0; i<words.size(); i++){
            if(!words.get(i).substring(0, 1).equals(s.substring(i, i+1))) {
                return false;
            }
        }
        return true;
    }
}
```
['String', 'Java']