异常处理帮助（Java）

Question

试图掌握异常处理，但我还不确定我是否理解。应该发生的事情是，如果用户输入的不是整数，则应该执行mismatchexception并打印该友好消息。此外，关于异常处理的主题，如果我的代码中有任何无用的例外，请告诉我（如果你不介意的话，为什么）。完整代码链接如下。谢谢！

public static void addRecords() {
    System.out.print("Hello, welcome to my magical program!\n");

    for (int i = 0; i < 10; i++) {
        System.out.printf("Please enter integer no. %d: ", i + 1);
        numbers[i] = input.nextInt();
        System.out.println();
        {
            try {
                output.format("Inputted integer: %s%n", String.valueOf(numbers[i]));
            } catch (FormatterClosedException formatterClosedexception) {
                System.err.println("Error writing to the file. Terminating.");
                break;
            } catch (InputMismatchException inputMismatchException) {
                System.err.println("Please restart the program and enter integers ONLY.");
                break;
            } catch (NoSuchElementException elementException) {
                System.err.println("Invalid input. Please try again.");
                input.nextLine();
            }
        }
    }
}

此处的完整代码： http://pastebin.com/eSGau5ax

Answer 1

<强>首先，

对于不包含整数类型数据的数据文件numbers.txt，会发生

try (BufferedReader br = new BufferedReader (new FileReader("numbers.txt"))){ 。请输入相关数据。它将解决此输入误码。 为了更好地理解，请遵循以下教程： https://examples.javacodegeeks.com/java-basics/exceptions/java-util-inputmismatchexception-how-to-solve-inputmismatchexception/

下一步，

使用此代码。它可能对你有帮助。

实际上您在http://pastebin.com/eSGau5ax中发布了什么。

有2个错误。

中发生了第一个错误

            try{
                BufferedReader br = new BufferedReader (new FileReader("numbers.txt"));

但我改变了它，因为有一些错误。

numbers[i] = input.nextInt();

另一个错误与获取输入部分有关必须在try catch中。但是我还没有运行你的代码。所有功劳都归功于其他SO助手。

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Formatter;
import java.util.FormatterClosedException;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;
import java.util.Scanner;
import java.nio.file.NoSuchFileException;

public class Average {

    private static Formatter output;

    static Scanner input = new Scanner(System.in);
    static int[] numbers = new int[10];

    public static void main(String[] args) {
        openFile();
        addRecords();
        closeFile();
        readRecords();
    }

    public static void openFile() {
        try {
            output = new Formatter("numbers.txt");
        } catch (SecurityException securityException) {
            System.err.println("Write permission denied. Terminating.");
            System.exit(1);
        } catch (FileNotFoundException fileNotFoundException) {
            System.err.println("Error opening file. Terminating.");
            System.exit(1);
        }
    }

    public static void addRecords() {
        System.out.print("Hello, welcome to my magical program!\n");
        try {
            for (int i = 0; i < 10; i++) {
                System.out.printf("Please enter integer no. %d: ", i + 1);
                numbers[i] = input.nextInt();
                System.out.println();
                output.format("Inputted integer: %s%n", String
                        .valueOf(numbers[i]));
            }
        } catch (FormatterClosedException formatterClosedexception) {
            System.err.println("Error writing to the file. Terminating.");
            break;
        } catch (InputMismatchException inputMismatchException) {
            System.err
                    .println("Please restart the program and enter integers ONLY.");
            break;
        } catch (NoSuchElementException elementException) {
            System.err.println("Invalid input. Please try again.");
            input.nextLine();
        }

    }

    public static void closeFile() {
        {
            if (output != null)
                output.close();
        }
    }

    public static void readRecords() {

        try {
            BufferedReader br = new BufferedReader(
                    new FileReader("numbers.txt"));
            String line;
            int[] number = new int[10];
            int i = -1;
            int sum = 0;
            double average = 0;

            while ((line = br.readLine()) != null) {
                i++;
                String[] split = line.split(":");
                line = split[1].trim();
                number[i] = Integer.parseInt(line);
                System.out.printf("Integer number %d: %d%n", i, numbers[i]);
                sum += number[i];
                average = (double) sum / 10;
            }

            System.out.printf("%nWould your sum happen to be %d? %n", sum);
            System.out.printf("Which means your average is: %.2f %n", average);

        } catch (NoSuchFileException noSuchFileException) {
            System.out
                    .print("This file was not created properly and cannot be found.");
        } catch (FileNotFoundException fileNotFoundException) {
            System.out
                    .print("I can't seem to find your file :( That's too bad...");
        } catch (IOException ioexception) {
            System.out
                    .print("Whoopsie daisy, you got yourself an IOException. Better luck next time!");
        } finally {
            System.out
                    .print("Check your numbers.txt file and see what ya got!");
        }
    }
}

现在您的代码看起来像

<ref local="authenticationManager" />

Answer 2

我建议从方法中抛出异常并在main方法中捕获它们。这些方法不应该决定如何处理异常，而是调用者（在这种情况下是主方法）决定是打印还是将其记录在文件中。

Answer 3

您正试图捕捉try之外发生的异常。 只需在try

中获取nextInt即可

public static void addRecords() {
    System.out.print("Hello, welcome to my magical program!\n");

    for (int i = 0; i < 10; i++) {
        System.out.printf("Please enter integer no. %d: ", i + 1);
        System.out.println();
        {
            try {
                numbers[i] = input.nextInt();
                output.format("Inputted integer: %s%n", String.valueOf(numbers[i]));
            } catch (FormatterClosedException formatterClosedexception) {
                System.err.println("Error writing to the file. Terminating.");
                break;
            } catch (InputMismatchException inputMismatchException) {
                System.err.println("Please restart the program and enter integers ONLY.");
                break;
            } catch (NoSuchElementException elementException) {
                System.err.println("Invalid input. Please try again.");
                input.nextLine();
            }
        }
    }
}