[java] 2744. 대소문자 바꾸기

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String input = br.readLine();
        //character 클래스 이용
        StringBuilder result = new StringBuilder();
        for (int i=0;i<input.length();i++) {
            char ch = input.charAt(i);
            if (Character.isUpperCase(ch)) {
                ch = Character.toLowerCase(ch);
            } else if (Character.isLowerCase(ch)) {
                ch = Character.toUpperCase(ch);
            }
            result.append(ch);
        }
        System.out.println(result.toString());
    }
}