public class Main {
    public static void main(String[] args) {
        String str = "pcTclnGloRgLrtLhgljkLhGFauPewSKgt";
        String str_1 = str.toUpperCase();//大写
        String str_2 = str.toLowerCase();//小写
        System.out.println(str_1);
        System.out.println(str_2);
        
    }
}

　结果= =是