寫入文本文件問題

Question

public static void makeSandwich()
{
    System.out.println("Enter First Name: ");
    String name = Scanner.next();
    double price = sandwich.getBreadPrice() + sandwich.getMeatPrice() + sandwich.getVegPrice();
    sandwich.setPrice(price);
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
    Date date = new Date();

    System.out.println(dateFormat.format(date) + " " + name + " " + sandwich.getBread() + " " + sandwich.getMeat() + " " + sandwich.getVegetables() + " " + currency.format(sandwich.getPrice()));
    OrderLine.writeOrderLine(name, sandwich.getBread(), sandwich.getMeat(), sandwich.getVegetables(), sandwich.getPrice());
}

這是我的orderline.app代碼

public class OrderLine{
    private static Sandwich sandwich = null;

    public static void writeOrderLine(String name, String bread, String meat, String veg, double price)
    {
        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        Date date = new Date();
        try
        {
            File productsFile = new File("orderline.txt");
            PrintWriter out = new PrintWriter(
                new BufferedWriter(
                new FileWriter(productsFile, true)));

           out.print(dateFormat.format(date) + "\t");
           out.print(name + "\t");
           out.print(sandwich.getBread() + "\t");
           out.print(sandwich.getMeat() + "\t");
           out.print(sandwich.getVegetables() + "\t");
           out.println(sandwich.getPrice() + "\t");
           out.close();
       }
       catch (IOException e)
       {
           System.out.println(e);
       }
    }
}

它根本不會打印，但是當我在orderline.java中的dateformat之前添加“ sandwich = new Sandwich（）”這一行時，它可以工作，但是由於我想創建一個新的三明治，最終卻給了我空字符串。 我怎么稱呼我已經做的三明治？

Answer 1

在writeOrderLine函數中，您尚未初始化三明治，但可以傳遞三明治的所有屬性，您可以按以下方式進行操作

 public static void writeOrderLine(String name, String bread, String meat, String veg, double price)
        {
            DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
            Date date = new Date();
            try
            {
                File productsFile = new File("orderline.txt");
                PrintWriter out = new PrintWriter(
                    new BufferedWriter(
                    new FileWriter(productsFile, true)));

               out.print(dateFormat.format(date) + "\t");
               out.print(name + "\t");
               out.print(bread + "\t");
               out.print(meat + "\t");
               out.print(veg + "\t");
               out.println(price+ "\t");
               out.close();
           }
           catch (IOException e)
           {
               System.out.println(e);
           }
        }

或者你可以這樣

這樣叫

OrderLine.writeOrderLine(name, sandwich);

並將功能更改為

public static void writeOrderLine(String name, Sandwich sandwich)
    {
        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        Date date = new Date();
        try
        {
            File productsFile = new File("orderline.txt");
            PrintWriter out = new PrintWriter(
                new BufferedWriter(
                new FileWriter(productsFile, true)));

           out.print(dateFormat.format(date) + "\t");
           out.print(name + "\t");
           out.print(sandwich.getBread() + "\t");
           out.print(sandwich.getMeat() + "\t");
           out.print(sandwich.getVegetables() + "\t");
           out.println(sandwich.getPrice() + "\t");
           out.close();
       }
       catch (IOException e)
       {
           System.out.println(e);
       }
    }