[string] 대소문자 변환

import java.util.*;
class Main {	
	public String solution(String str){
		String answer="";
		for(char x : str.toCharArray()){
			if(Character.isLowerCase(x)) answer+=Character.toUpperCase(x);
			else answer+=Character.toLowerCase(x);

		}
		return answer;
	}

	public static void main(String[] args){
		Main T = new Main();
		Scanner kb = new Scanner(System.in);
		String str=kb.next();
		System.out.print(T.solution(str));
	}
}

 

import java.util.*;
class Main {	
	public String solution(String str){
		String answer="";
		for(char x : str.toCharArray()){
			if(x>=97 && x<=122) answer+=(char)(x-32);
			else answer+=(char)(x+32);
		}
		return answer;
	}

	public static void main(String[] args){
		Main T = new Main();
		Scanner kb = new Scanner(System.in);
		String str=kb.next();
		System.out.print(T.solution(str));
	}
}

toCharArray : string이 문자배열로 전환됨
isLowerCase : x가 소문자인가? 묻고 소문자일시 참
소문자일때 누적, 대문자일땐 tolowercase로 바꾸어 누적