Java-创建菜单时，扫描仪出现文本文件错误

Question

我对Java和编程领域还是陌生的，并且一直在从事学校作业，我似乎无法弄清楚。我不断收到如下错误：

Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at assignments.DonationTextFiles.menu(DonationTextFiles.java:30)
at assignments.DonationTextFiles.main(DonationTextFiles.java:206)

我正在尝试创建一个菜单，用户在其中输入int值以选择选项，并在方法运行后重复菜单。菜单方法现在看起来像这样：

package assignments;


import java.util.Scanner ; 
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintWriter;



public class DonationTextFiles

    {

    public static void menu(){
        Scanner keyboard = new Scanner (System.in);
        int input = 0;

        while(true) {

        System.out.println("Choose and option for the menu");
        System.out.println( "1. Create a file \n"+
                            "2. Append to the file \n" +
                            "3. Print the file \n" +
                            "4. Locate the largest donation\n" +
                            "0. Exit Program \n" +
                            "Make a selection");
            input = keyboard.nextInt();

            switch(input){
                case 0:
                    System.out.println("End Processing");
                    System.exit(0);
                     break;
                case 1:
                     createFile();
                     break;
                case 2:
                     appendFile();
                     break;
                case 3:
                     printFile();
                     break;
                case 4:
                     locateHighest();
                     break;

                default:
                    System.out.println("Please enter a number between 0 and 4");
                    break;
            }

        }   

}



    public static void locateHighest()
    {
        System.out.println("I will read from the text file Donations.txt and display it to the console");
        Scanner inputStream = null;
    try
    {
        inputStream = new Scanner (new FileInputStream("Donations.txt"));
    }
    catch (FileNotFoundException e)
    {
        System.out.print("Donations.txt was not found");
        System.out.println(" or could not be opened");
        System.exit(0);
    }


        String name = inputStream.nextLine ();
        double amount = inputStream.nextDouble();
        double temp = 0;

        while(inputStream.hasNext()) {

            if(temp > inputStream.nextDouble()) {


            }else {
                temp = inputStream.nextDouble();
            }

            name = inputStream.nextLine ( );
            amount = inputStream.nextDouble();

            if(!inputStream.hasNext()){
                if(temp < inputStream.nextDouble()) {
                    temp = inputStream.nextDouble();

                }
            }
        }


        inputStream.close();
        System.out.println(temp);



}



    public static void createFile()
    {
        PrintWriter outputStream = null;
        try
        {
        outputStream = new PrintWriter (new FileOutputStream("Donations.txt"));
        }
        catch (FileNotFoundException e)
        {

        System.out.println("Error opening the file Donations.txt");
        System.exit(0);
        }

        System.out.println("Creating a file");

        outputStream.close();
        System.out.println("End of processing");

        }

    public static void printFile()
    {
        System.out.println("I will read from the text file Donations.txt and display it to the console");
        Scanner inputStream = null;
    try
    {
        inputStream = new Scanner (new FileInputStream("Donations.txt"));
    }
    catch (FileNotFoundException e)
    {
        System.out.print("Donations.txt was not found");
        System.out.println(" or could not be opened");
        System.exit(0);
    }

        String line = inputStream.nextLine ( );
        double amount = inputStream.nextDouble();

        System.out.println("Name" + "\t\t" + "Donation");

    while(inputStream.hasNext()) {

        System.out.println(line + "\t\t"+ amount); 

        line = inputStream.nextLine ( );
        amount = inputStream.nextDouble();

        if(!inputStream.hasNext()){
            System.out.println(line + "\t\t"+ amount); 
        }
    }


    inputStream.close();
    System.out.println("End of processing");


}

    public static void appendFile()
    {
        PrintWriter outputStream = null;
    try
    {
        outputStream = new PrintWriter (new

            FileOutputStream ("Donations.txt", true));

    }
    catch (FileNotFoundException e)
    {
        System.out.println ("Error opening the file Donations.txt");

        System.exit(0);
    }
        Scanner keyboard = new Scanner(System.in);
        String name = ""; double amount = 0.0;
        System.out.println("Enter the donor name and amount of donation");

        name = keyboard.nextLine();
        amount = keyboard.nextDouble();
        outputStream.println(name);
        outputStream.println(amount);
        outputStream.close();
        keyboard.close();
    System.out.println("End of Append Processing");


}


        public static void main(String[ ] args)
        {
            menu();

    }


}  

}

我会得到这样的输出，所以

当我尝试使用appendFile（）将项目追加到文本文件时，会出现问题。它会追加，但菜单无法再次运行。 createFile（）似乎可以正常运行两次。我认为Scanner以及我的使用方式应该有问题。有人可以帮我吗？

Answer 1

在系统退出之前，请不要关闭扫描仪。也许可以在“ System.exit（0）;”之前的“ 0”案例语句中执行此操作。