编写一个程序，实现字符串大小写的转换并倒叙输出

String str = "HelloWorld";
char[] chars = str.toCharArray();
StringBuffer stringBuffer = new StringBuffer();
for (int a = chars.length - 1; a > -1; a--){
     // 小写为false
     boolean upperCase = Character.isUpperCase(chars[a]);
     if (upperCase){
           stringBuffer.append((chars[a] + "").toLowerCase());
     }else{
           stringBuffer.append((chars[a] + "").toUpperCase());
     }
}
System.out.println(stringBuffer.toString());

public class test {
    public static void main(String[] args) {
        StringBuffer stringBuffer=new StringBuffer();
        String z="HelloWorld";
        for (int zin=z.length()-1;zin>=0;zin--){
            if(97<=(int)z.charAt(zin)&&122>=(int)z.charAt(zin)){
                stringBuffer.append((z.charAt(zin)+"").toUpperCase());
            }
            if(65<=(int)z.charAt(zin)&&90>=(int)z.charAt(zin)){
                stringBuffer.append((z.charAt(zin)+"").toLowerCase());
            }
        }
        System.out.println(stringBuffer.toString());
    }
}