Proper use of Scanner.hasNextLine in Java?

Question

I'm currently working on a project for my class in which I have to sort an array which is numbers in a text file. I have created a reader to see how many values I have in the .txt file so I can define my array size, but my while() statement seems to be broken and goes in a never ending loop when using .hasNextLine. Here is my code:

    File unsorted = new File("unsorted.txt");

    int j = 0;//Counter for the amount of slots in the array

    System.out.println("Executing file reading...");

    try
    {

        Scanner input = new Scanner(unsorted);

        while(input.hasNextLine()){

            j++;//Scanner to count the length of the array

            System.out.println(j);

        }

        input.close();

        System.out.println("The file has " + j + " lines.");

    }
    catch (IOException ex){

        System.out.printf("ERROR: Could not read file 'unsorted.txt'", ex);

    }

    System.out.println("File read.");

My print line after the try{} doesn't ever print, instead when I have the J print within the while() loop, it goes on forever. The file has 7 values inside of it for now, all numbers.

You never read the line. Just check if it has more lines. So it keeps saying "yes" because it's still on the first line. — RealSkeptic, Nov 14 '16 at 15:04
Possible duplicate of http://stackoverflow.com/questions/8352040/scanner-on-text-file-hasnext-is-infinite — Niranjan Kumar, Nov 14 '16 at 15:06

score 1 · Answer 1 · answered Nov 14 '16 at 15:06

1

The value of the hasNextLine() method only changes -- only has the chance to change -- when you call nextLine(). The nextLine() method gives you the content of the line, and it advances the Scanner by one line.

answered Nov 14 '16 at 15:06

Drew Wills

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Proper use of Scanner.hasNextLine in Java?

1 Answers1