使用子字符串java分隔数字

Question

我想用 Java 创建一个程序，从 user_input 获取数字并使其成为货币格式......这是我的代码package Seperator_checker;import java.util.Scanner;public class Seperator {    public static void main(String[] args) {        Scanner number=new Scanner(System.in);        System.out.print("Please Enter Your Number: ");        String user_number=number.next();        if(user_number.length()> 3) {            user_number=user_number.substring(0,user_number.length()-3) + "," + user_number.substring(0,1);            System.out.println("________________________________________");            System.out.println("Your Currency Number Is: "+ user_number);        }    }}