Printwriter输出不接受.printf格式化程序到文件？

Question

使用以下代码输出到已建立的文件时：

import java.util.Scanner;
import java.io.*;
public class BarakProductOrder
{
    public static void main(String[] args) throws IOException
    {
        //Establish scanner object
        Scanner input = new Scanner (System.in);

        //Declare variables
        String name, product, street, city, state, zip;
        int qty;
        double price;

        //Collect data
        System.out.println("Welcome to Matt's Dog Food Emporium!\n\nWhat is your name?");
        name = input.nextLine();

        System.out.println("Which product would you like to order today?");
        product = input.nextLine();

        System.out.println("How many would you like?");
        qty = input.nextInt();
        price = 4.56*qty;

        input.nextLine(); //Must be placed to not skip over "address" line

        System.out.println("Enter your street address:");
        street = input.nextLine();

        System.out.println("Enter the City:");
        city = input.nextLine();
        System.out.println("Enter the State (ex.: NY):");
        state = input.nextLine();
        System.out.println("Enter the Zip:");
        zip = input.nextLine();

        System.out.println("Thank you for your order, " + name);

        //Output data to file "BarakOrder.txt"
        PrintWriter outputFile = new PrintWriter("C:\\Users\\fbara\\Desktop\\CISS 110\\BarakOrder.txt");
        outputFile.println("Order Number: 001");
        outputFile.println("Product: " + product);
        outputFile.println("Quantity: " + qty);
        outputFile.printf("Price = 4.56*" + qty + " = $" + "%.2f" + price);
        outputFile.println("Customer Contact Info: " + name);
        outputFile.println("Address: " + street);
        outputFile.println(city + ", " + state + " " + zip);

        //Close scanner and file object
        input.close();
        outputFile.close();
        System.out.println("Data has been written.");
    }
}

在第45行使用“％。2f”修饰符给出以下错误消息：

java.util.MissingFormatArgumentException：java.io.PrintWriter.formaf（未知来源）java.io.PrintWriter.format（未知来源）的java.util.Formatter.format（未知来源）格式说明符'％。2f'at BarakProductOrder.main（BarakProductOrder.java:45）at sun.reflect.NativeMethodAccessorImpl.invoke0（Native Method）at sun.reflect.NativeMethodAccessorImpl.invoke（Unknown Source）at sun.reflect.DelegatingMethodAccessorImpl.invoke（Unknown Source）at java.lang edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(javacCompiler.java:267）中的.reflect.Method.invoke（未知来源）

我在outputFile.printf上使用了错误的修饰符吗？或错误的“.print（）”行？

Answer 1

这不是printf的工作方式;你给它一个格式然后打印的东西。

你没有传递任何格式的%.2f，你试图添加它。文档提供了有关如何使用它的信息（世界上有很多例子）。

大致：

outputFile.printf("Price = 4.56*" + qty + " = $" + "%.2f", price);

虽然我不确定为什么你不会为qty做同样的格式化。