java - 需要帮助在 java 中创建文件

Question

我需要创建一个文件，但没有创建一个文件，而且我不知道哪里出了问题

这是我创建的文件名文本的位置

public class LetterGradeDisplayer {
    public static void main(String[] args) {
        LetterGradeConverter conv1 = new LetterGradeConverter("c://temp//grade1.txt", 6);
        System.out.println("Contents: ");
        System.out.println(conv1);

        LetterGradeConverter conv2 = new LetterGradeConverter("c://temp//grade2.txt", 6);
        System.out.println("Contents: ");
        System.out.println(conv2);

这是获取文件名参数的地方

public LetterGradeConverter(String fileName, int maxGrade) {
    File file = new File(fileName);
    int Grade[] = new int [maxGrade];
    actualLength = maxGrade;
    char LetterGradeList[] = new char [maxGrade];

    int count = 0;
    Scanner scan;
    try {
        scan = new Scanner(file);
        while(scan.hasNextInt()) {
            Grade[count] = scan.nextInt();
            count++;
        }
        scan.close();
    }
    catch(FileNotFoundException e) {
        e.printStackTrace();
    }

    GradeConverter();

这是我收到的错误文本:

java.io.FileNotFoundException: c:\temp\grade1.txt (The system cannot find the file specified)
    at java.base/java.io.FileInputStream.open0(Native Method)
    at java.base/java.io.FileInputStream.open(Unknown Source)
    at java.base/java.io.FileInputStream.<init>(Unknown Source)
    at java.base/java.util.Scanner.<init>(Unknown Source)
    at LetterGrade.LetterGradeConverter.<init>(LetterGradeConverter.java:21)
    at LetterGrade.LetterGradeDisplayer.main(LetterGradeDisplayer.java:7)
Exception in thread "main" java.lang.NullPointerException
    at LetterGrade.LetterGradeConverter.GradeConverter(LetterGradeConverter.java:36)
    at LetterGrade.LetterGradeConverter.<init>(LetterGradeConverter.java:32)
    at LetterGrade.LetterGradeDisplayer.main(LetterGradeDisplayer.java:7)

Answer 1

您提到未创建文件，但我在您的代码中没有看到任何应该创建文件的内容。

您是否期望 new File() 为您在文件系统上创建文件？因为它不会，为此你需要 File#createNewFile