java - 如果我希望能够在文件 "total sales"中显示 "Cart.txt"，我该怎么做？

Question

我希望 Cart.txt 文件能够写入文件本身中的总销售额。现在的文件只是说:

3,2,Shoes
3,4,Shirt
2,5,Car

这是当前的输出:

run:
Enter how many items you are buying
3
Enter the items you are buying, structured as followed 
Quantity,Price,Item Name:
3,2,Shoes
3,4,Shirt
2,5,Car
Those values were written to Cart.txt
Sold 3 of Shoes at $2.00 each. 
Sold 3 of Shirt at $4.00 each. 
Sold 2 of Car at $5.00 each. 
Total sales: $28.00

这是代码本身:

package shop;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.File;
import java.io.PrintWriter;
import java.util.Scanner;

public class Shop 
{

public static void main(String[] args)
{
    String fileName = "Cart.txt";
    PrintWriter outputStream = null;

    try
    {
        outputStream= new PrintWriter (fileName);
    }
    catch (FileNotFoundException e)
    {
        System.out.println("Error opening the file "+ fileName);
        System.exit(0);
    }

    System.out.println("Enter how many items you are buying");
    Scanner keyboard = new Scanner (System.in);
    Scanner intinput = new Scanner (System.in);
    int input = intinput.nextInt();

    System.out.println("Enter the items you are buying, structured as followed"
            + " \nQuantity,Price,Item Name:");


    for(int count=1; count<=input; count++)
    {
        String line = keyboard.nextLine();
        outputStream.println(line);

    }

    outputStream.close();
    System.out.println("Those values were written to "+ fileName);

    try
    {
        Scanner inputStream = new Scanner(new File(fileName));
        String line = inputStream.toString();
        double total = 0;
    for(int count=1; count<=input; count++)
    {

            line = inputStream.nextLine();
            String[] ary = line.split (",");
            int quantity = Integer.parseInt (ary[0]);
            double price = Double.parseDouble(ary[1]);
            String description = ary[2];
            System.out.printf("Sold %d of %s at $%1.2f each. \n",
                    quantity, description, price);
            total += quantity * price;  

    }

        System.out.printf("Total sales: $%1.2f\n", total);
        inputStream.close();

    }
    catch (FileNotFoundException e)
    {
        System.out.println("Cannot find file " + fileName);
    }
    catch (IOException e)
    {
        System.out.println("Problem with input file " + fileName);
    }

}
}

Answer 1

执行以下操作:

1. 计算总数后写入文件:outputStream.println(总计);
2. 将总计写入文件后关闭outputStream

<小时/>

编辑:

在此代码块中进行以下更改:

    System.out.println("Enter the items you are buying, structured as 
                        followed" + " \nQuantity,Price,Item Name:");
    double tot = 0.0;
    for (int count = 1; count <= input; count++) {
        String line = keyboard.nextLine();
        outputStream.println(line);
        String[] arr = line.split(",");
        tot += (Integer.parseInt(arr[0]) * Double.parseDouble(arr[1]));
    }
    outputStream.println("Total sales: $" + tot);
    outputStream.close();
    System.out.println("Those values were written to " + fileName);

这里我们计算所有条目的总数，然后将其写入文件一次。

输出

3,2,Shoes

3,4,Shirt

2,5,Car

Total sales: $28.0