描述：

输入一个整数，将这个整数以字符串的形式逆序输出

程序不考虑负数的情况，若数字含有0，则逆序形式也含有0，如输入为100，则输出为001

package test;import java.util.Scanner;public class exam03 {    public static void main(String[] arg) {        int b;        Scanner scanner = new Scanner(System.in);        while (scanner.hasNext()) {            int n = scanner.nextInt();            System.out.println(reverseNum1(n));            System.out.println(reverseNum2(n));            System.out.println(reverseNum3(n));        }    }    public static StringBuilder reverseNum1(int a) {        // 方法1        StringBuilder sb = new StringBuilder(a + "");// 将a转换成字符串        sb.reverse();        return sb;    }    public static String reverseNum2(int a) {        // 方法2:取整数，转换成字符串，再把每个字符存入StringBuilder中，最后转换成字符串输出        String s = String.valueOf(a);        StringBuilder sbBuilder = new StringBuilder();        for (int i = s.length() - 1; i >= 0; i--) {            sbBuilder.append(s.charAt(i));        }        return sbBuilder.toString();    }    public static String reverseNum3(int a) {        // 方法3        String s = "";        while (a != 0) {            int n = a % 10;            s = s + n;            a /= 10;        }        return s;    }}