以下代碼僅供參考：
import java.util.Scanner;

public class CalcMoney {

private double total_money;
private int count;
private double price;
Scanner s = new Scanner(System.in);

public CalcMoney() {
  System.out.print(你想输入几个商品?);
  int c = s.nextInt();
  this.foo(c);
}
private void foo(int c)
{
  for(int i =0; i < c; i ++)
  {
   System.out.print(input nubmer + (i + 1) +号商品的单价:);
   price = s.nextDouble();
   System.out.print(input nubmer + (i + 1) +号商品的数量:);
   count = s.nextInt();
   total_money += price * count;
  }
  System.out.println(商品总价: + total_money * 0.8 );
 
  System.out.print(实收金额:);
  double m = s.nextDouble();
  double d = m - Math.ceil(total_money * 0.8);
  System.out.println( m + +d);
  System.out.print(应找: + d);
}

public static void main(String[] args) {
  new CalcMoney();
}
}