java String反转

这里提供了四种算法（其它的就不列举了）

    public static String convert1(String str) {
        if (str == null || str.isEmpty()) {
            return str;
        }

        char a[] = str.toCharArray();
        int halfSize = a.length >> 1;
        char temp;

        for (int i = 0; i < halfSize; i++) {
            temp = a[i];
            a[i] = a[a.length - i - 1];
            a[a.length - i - 1] = temp;
        }

        return new String(a);
    }

    //递归
    public static String convert2(String str) {
        if (str == null || str.isEmpty()) {
            return str;
        }

        StringBuffer sb = new StringBuffer(convert2(str.substring(1)));
        return sb.append(str.charAt(0)).toString();
    }

    public static String convert3(String str) {
        if (str == null || str.isEmpty()) {
            return str;
        }

        StringBuffer sb = new StringBuffer("");
        int size = str.length();
        for (int i = 0; i < size; i++) {
            sb.append(str.charAt(size - i - 1));
        }

        return sb.toString();
    }

    public static String convert4(String str) {
        if (str == null) {
            return str;
        }
        
        StringBuffer sb = new StringBuffer(str);
        return sb.reverse().toString();
    }

    public static void main(String t[]) {
        System.out.println(convert4("123456"));
    }