[프로그래머스] 오픈채팅방

import java.util.*;
/*
Enter uid1234 Muzi
Leave uid4567 
Change uid1234 Muzi
*/

class Solution {
    public String[] solution(String[] record) {
        // id - nickname hashmap : Enter, Change
        String[] answer = {};
        Map<String, String> id_nick = new HashMap<>();
        
        for(String s : record){
            String[] temp = s.split(" ");
            if(temp[0].equalsIgnoreCase("Enter") || temp[0].equalsIgnoreCase("Change")){

                id_nick.put(temp[1], temp[2]);
            }
        }

        List<String> ans = new ArrayList<>();
        
        for(String s : record){
            
            String[] temp = s.split(" ");

            switch(temp[0]){
                case "Enter":
                    ans.add(id_nick.get(temp[1]) + "님이 들어왔습니다.");
                    break;
                case "Leave":
                    ans.add(id_nick.get(temp[1]) + "님이 나갔습니다.");
                    break;
            }
        }
        int ansSize = ans.size();      
        answer = ans.toArray(new String[ansSize]);

        return answer;
    }
}