为什么我看不到我的文本文件？

Question

I am trying to read in a text file, but I keep getting "java.util.InputMismatchException".

Main class:

dc.loadData(new File("DVDCollection.txt"));

Class that reads/loads the files data:

Scanner inputFile = null;
public void loadData(File fileName) {
    try {
        inputFile = new Scanner (new File("DVDCollection.txt"));
    }

    catch (Exception FileNotFoundException) {
        System.out.println("ERROR: " + FileNotFoundException.getMessage());
        System.exit(1);
    }

    while (inputFile.hasNext()) {

        String fileTitle = inputFile.nextLine();
        String fileCategory = inputFile.nextLine();
        String fileRunningTime = inputFile.nextLine();
        int fileYear = inputFile.nextInt();
        double filePrice = inputFile.nextDouble();

        DVD dvdEntry = new DVD(fileTitle, fileCategory, fileRunningTime, fileYear, filePrice);
        DVDlist.add(dvdEntry);
    }
    inputFile.close();
}

The text file has one piece of information per line, with no line breaks.

Example:

Movie title1 (Sttring)
movie category1 (String)
movie duration1 (String)
movie year1 (int)
movie price1 (double)
Movie title2
movie category2
movie duration2
movie year2
movie price2
etc
etc...

And here is an actual example of what it's supposed to read in:

Adam
Documentary
78 minutes
2012
7.99
Choo Choo
Documentary
60 minutes
2006
11.99

What the error says:

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextDouble(Unknown Source)
at XXXX_XXXX.DVDCollection.loadData(DVDCollection.java:29)
at XXXX_XXXX.DVDApplication.main(DVDApplication.java:14)

Answer 1

You probably have an issue with those lines:

int fileYear = inputFile.nextInt();
double filePrice = inputFile.nextDouble();

At some point the expected type is not found (not a double). Make sure you go to the next line and that your file contains no errors (numbers are formatted as expected...).

Answer 2

The InputMisMatchException (when thrown from nextDouble() ), indicates that "the next token does not match the Float regular expression, or is out of range" (quote from Javadoc ).

So the problem is most likely in the file you're trying to read. Without its contents, however, it's hard to guess what exactly is the culprit.

Answer 3

Scanner#nextDouble() throws InputMismatchException - if the next token does not match the Float regular expression, or is out of range.

So clearly the input is not a float literal. I am expecting there might be space, which makes double as string ..

Answer 4

From your trace shows that the Scanner has tried to read a value that is supposed to be double value is not a double value.

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
**at java.util.Scanner.nextDouble(Unknown Source)**
at XXXX_XXXX.DVDCollection.loadData(DVDCollection.java:29)
at XXXX_XXXX.DVDApplication.main(DVDApplication.java:14)

Answer 5

In your case it will suit

String fileTitle = inputFile.nextLine();
String fileCategory = inputFile.nextLine();
String fileRunningTime = inputFile.nextLine();
int fileYear = Integer.parseInt(inputFile.nextLine());
double filePrice = Double.parseDouble(inputFile.nextLine());

Answer 6

I found the reason for your problem.

When you use nextline() it advances the scanner past the current line and places it at the beginning of next line.

But when you use nextInt or nextDouble then the scanner is advanced just past the nextInteger and next double value and placed at the end of the current line itself.

Hence a \\n is also read as part of the next nextLine breaking the sequence.

You can code like this as a work around.

while (inputFile.hasNext()) {
            String fileTitle = inputFile.nextLine();
            String fileCategory = inputFile.nextLine();
            String fileRunningTime = inputFile.nextLine();
            int fileYear = Integer.parseInt(inputFile.nextLine());
            double filePrice = Double.parseDouble(inputFile.nextLine());
        }
        inputFile.close();

Answer 7

Just add the line marked with ***
while (inputFile.hasNext()) {

    String fileTitle = inputFile.nextLine();
    String fileCategory = inputFile.nextLine();
    String fileRunningTime = inputFile.nextLine();
    int fileYear = inputFile.nextInt();
    double filePrice = inputFile.nextDouble();

    DVD dvdEntry = new DVD(fileTitle, fileCategory, fileRunningTime,
        fileYear, filePrice);
    DVDlist.add(dvdEntry);

    if (inputFile.hasNext()) //***
        inputFile.nextLine();
}