[Java] 대소문자 변환

[방법1]

import java.util.*;

public class Main {
	public String solution(String str) {
		String answer = "";

		for (char c : str.toCharArray()) {
			if (65 <= c && c <= 90) {
				c += 32;
			} else if (97 <= c && c <= 122) {
				c -= 32;
			}
			answer += c;
		}

		return answer;
	}

	public static void main(String[] args) {
		Main M = new Main();
		Scanner scan = new Scanner(System.in);

		String str = scan.next();
		System.out.print(M.solution(str));
		scan.close();

		return;
	}
}

* 대문자 char 에서 32 를 더하면 소문자 char
* 소문자 char 에서 32를 빼면 대문자 char

[방법2]

import java.util.*;

public class Main {
	public String solution(String str) {
		String answer = "";

		for (char c : str.toCharArray()) {
			if (Character.isLowerCase(c)) {
				c = Character.toUpperCase(c);
			} else if (Character.isUpperCase(c)) {
				c = Character.toLowerCase(c);
			}
			answer += c;
		}

		return answer;
	}

	public static void main(String[] args) {
		Main M = new Main();
		Scanner scan = new Scanner(System.in);

		String str = scan.next();
		System.out.print(M.solution(str));
		scan.close();

		return;
	}
}