완주하지 못한 선수

import java.util.HashMap;
import java.util.Map.Entry;
 
class Solution {
    public String solution(String[] participant, String[] completion) {
        String answer = "";
        
        HashMap<String, Integer> map = new HashMap<>();
        for(String part : participant) {
            if(map.get(part) == null) {
                map.put(part, 0);
            }
            else
                map.put(part, map.get(part) + 1);
        }
        for(String com : completion)
            map.put(com, map.get(com) -1);
        
        for(Entry<String, Integer> entry : map.entrySet()) {
            if(entry.getValue() == 0)
                answer = entry.getKey();
        }
        
        return answer;
        
    }
}