用递归的方式把字符串倒转

package com.leecode;

public class Main {
    public static void main(String[] args) {
        String s = "123";
        System.out.println("reString(s) = " + reString(s));
    }

    public static String reString(String ss){
        if(ss==null || ss.length()<=1){
            return ss;
        }
        return reString(ss.substring(1))+ss.charAt(0);
    }
}