写出一个java程序：判断一个字符串是否是对称字符串，例如"abc"不是对称字符串，"aba"、"abba"、"aaa"、"mnanm"是对称字符串，分别使用(String和StringBuffer实现这个功能。

使用 String 实现：

public class StringSymmetry {
    public static boolean isSymmetry(String s) {
        int length = s.length();
        for (int i = 0; i < length / 2; i++) {
            if (s.charAt(i) != s.charAt(length - i - 1)) {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        String s1 = "abc";
        String s2 = "aba";
        String s3 = "abba";
        String s4 = "aaa";
        String s5 = "mnanm";

        System.out.println(s1 + " isSymmetry: " + isSymmetry(s1));
        System.out.println(s2 + " isSymmetry: " + isSymmetry(s2));
        System.out.println(s3 + " isSymmetry: " + isSymmetry(s3));
        System.out.println(s4 + " isSymmetry: " + isSymmetry(s4));
        System.out.println(s5 + " isSymmetry: " + isSymmetry(s5));
    }
}

使用 StringBuffer 实现：

public class StringBufferSymmetry {
    public static boolean isSymmetry(String s) {
        StringBuffer sb = new StringBuffer(s);
        return s.equals(sb.reverse().toString());
    }

    public static void main(String[] args) {
        String s1 = "abc";
        String s2 = "aba";
        String s3 = "abba";
        String s4 = "aaa";
        String s5 = "mnanm";

        System.out.println(s1 + " isSymmetry: " + isSymmetry(s1));
        System.out.println(s2 + " isSymmetry: " + isSymmetry(s2));
        System.out.println(s3 + " isSymmetry: " + isSymmetry(s3));
        System.out.println(s4 + " isSymmetry: " + isSymmetry(s4));
        System.out.println(s5 + " isSymmetry: " + isSymmetry(s5));
    }
}