StringBuffer .Append()方法

package leixifeng;

import java.util.Scanner;

public class Yanzheng {

    public static void main(String[] args) {
        
        Scanner input = new Scanner(System.in);
        System.out.println("请输入金额");
        String nums = input.next();
        StringBuffer str =new StringBuffer(nums);
        for(int i = str.length()-3; i > 0 ; i-=3){
            str.insert(i, ‘,‘);
        }
        System.out.println(str);
    }

}
//StringBuffer 字符串的连接效率比String类高