Java Scanner hasNextLine NoSuchElementException？

Question

I am trying to read a large csv file line by line in order to find the number of occurences of a string in it.

Here is the code doing it :

public int getOffset(File file, String searched) throws FileNotFoundException {
    Scanner scanner = new Scanner(file).useDelimiter(System.getProperty("line.separator"));
    int occurences = 0;
    while (scanner.hasNextLine()) {
        String s = scanner.next();
        if (s.indexOf(searched) >= 0) {
            occurences++;
        }
    }
    return occurences;
}

However, after it has read the last line of the file, it checks one more time the while condition, and exits with this exception :

java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:838)
at java.util.Scanner.next(Scanner.java:1347)
at fr.sgcib.cva.mat.MatWriter.getOffset(MatWriter.java:83)
at fr.sgcib.cva.mat.MatWriter.writeFooter(MatWriter.java:71)
at fr.sgcib.cva.mat.NettingNodeHierarchyExtract.getLeNodes(NettingNodeHierarchyExtract.java:65)
at fr.sgcib.cva.mat.Mat.main(Mat.java:55)

Why doesn't it detect it's the end of the file ?

Answer 1

Use String s = scanner.nextLine(); instead of String s = scanner.next();

That means that your code would look like this:

public int getOffset(File file, String searched) throws FileNotFoundException {
    Scanner scanner = new Scanner(file).useDelimiter(System.getProperty("line.separator"));
    int occurences = 0;
    while (scanner.hasNextLine()) {
        String s = scanner.nextLine();
        if (s.indexOf(searched) >= 0) {
            occurences++;
        }
    }
    return occurences;
}

In general, when using Scanner your has... condition needs to match the next... data retrieval method

Answer 2

You are checking for the existence of the next line and scanning the next word. Either change the condition in while to while(scanner.hasNext()) or the scan line to String s = scanner.nextLine() .

Try this:

public int getOffset(File file, String searched) throws FileNotFoundException {
    Scanner scanner = new Scanner(file).useDelimiter(System.getProperty("line.separator"));
    int occurences = 0;
    while (scanner.hasNext()) {
        String s = scanner.next();
        if (s.indexOf(searched) >= 0) {
            occurences++;
        }
    }
    return occurences;
}

or

public int getOffset(File file, String searched) throws FileNotFoundException {
    Scanner scanner = new Scanner(file).useDelimiter(System.getProperty("line.separator"));
    int occurences = 0;
    while (scanner.hasNextLine()) {
        String s = scanner.nextLine();
        if (s.indexOf(searched) >= 0) {
            occurences++;
        }
    }
    return occurences;
}