字符串倒序並改變大小寫

public class TestRevent {
	public static void main(String[] args) {
		String s = "AaBCdFJk";
		StringBuffer sb = new StringBuffer();
		for (int i = s.length() - 1; i > -1; i--) {
			char s2 = s.charAt(i);

			//前提是判斷是否字符串
			if (Character.isLetter(s2)) {
				if (Character.isLowerCase(s2)) {
					s2 = Character.toUpperCase(s2);
				} else {
					s2 = Character.toLowerCase(s2);
				}
			}
			sb.append(s2);
		}
		System.out.print(sb);
		System.out.println();
		System.out.println(s);
	}

}