Question

我编写了一个应该使用BufferedReader和FileReader类读取外部文件的程序。它可以识别文件并成功构建，但它不会打印出它应该执行的文本文件的内容。这是代码：

程序

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class Lab9 {

    public static void main(String[] args) {

        BufferedReader reader = null;
        String line;
        Scanner sc = new Scanner(System.in);

        System.out.println("Please enter a file name to read");

        try {
            reader = new BufferedReader(new FileReader("C:\\Users\\Lee\\Documents\\NetBeansProjects\\Lab9\\" + sc.next()));
        } catch (FileNotFoundException ex) {

            System.out.println(ex.getMessage() + "File was not found");        

            try { 
                while ((line = reader.readLine()) != null)
                {
                    System.out.println(line);
                }
            } catch (IOException ex2) {
                System.out.println(ex2.getMessage() + "File did not read correctly");
            } finally {
                System.exit(0);
            }
        }
    }
}

应打印出来的文件内容如下所示：

文件内容

By what initials was Franklin Roosevelt better known?:FDR
Which number president was Franklin Roosevelt?:32
Which state was Franklin Roosevelt born in?:New York
In which year did Roosevelt become Governor of New York?:1929
What was the name of Franklin Roosevelt's wife?:Eleanor
How many children did Franklin Roosevelt have?:6
From which university did Franklin Roosevelt graduate with an A.B in history?:Harvard
What was the first name of Franklin Roosevelt's 5th cousin, who was also President?:Theodore
Which disease is believed to be the causes of Franklin Roosevelt's paralysis?:Polio
At what age did Franklin Roosevelt die?:63

实际输出

Please enter a file name to read
Questions.txt
BUILD SUCCESSFUL (total time: 6 seconds)

非常感谢有关解决此问题的任何帮助，谢谢。

Answer 1

您已尝试在FileNotFoundException的异常分支中读取该文件。这意味着，您的程序只有在找不到文件时才会读取文件，这没有任何意义。它的工作原理如下：

public static void main(String[] args) {

    BufferedReader reader = null;
    String line;
    Scanner sc = new Scanner(System.in);

    System.out.print("Please enter a file name to read: ");

    try {

        reader = new BufferedReader(
                new FileReader("C:\\Users\\Lee\\Documents\\NetBeansProjects\\Lab9\\" + sc.next()));

        try {

            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }

        } catch (IOException ex) {
            System.out.println(
                    ex.getMessage() + "File did not read correctly");
        } finally {
            try {
                if (reader != null)
                    reader.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

    } catch (FileNotFoundException ex) {
        System.out.println("File was not found.");
    }

}

作为旁注，您应该始终关闭您使用的资源，在这种情况下，您的文件由FileReader打开，如上面finally分支所示。此外，您无需致电System.exit(0)。

Answer 2

第一个catch语句没有结束括号，因此文件阅读器位于catch语句中。

Answer 3

FileNotFoundException

Answer 4

public static void main(String[] args) throws IOException {

        BufferedReader reader = null;
        String line;
        Scanner sc = new Scanner(System.in);
        System.out.println("Please enter a file name to read");
            reader = new BufferedReader(new FileReader(
                    "C:\\Users\\Lee\\Documents\\NetBeansProjects\\Lab9\\"
                            + sc.next()));
                while ((line = reader.readLine()) != null) {
                    System.out.println(line);
                }
        }

使用BufferedReader和FileReader;文件正在读取但不输出其内容？

4 个答案: