Contents of array being overwritten

Question

Please forgive me as I am new to all this. My code reads a text file of numbers and names. 3 sets of numbers after each name, each set of 3 gets put into an array. When the array gets sent to another class in the loop, the contents of the array becomes overwritten, I am assuming because it is just referencing the address of the array, not the actual values.

        public void readMarksData(String fileName) throws FileNotFoundException
{
    File dataFile = new File(fileName);
    Scanner scanner = new Scanner(dataFile);

    int[] marks = new int[3];
    scanner.nextLine();

    int i = 0;
    while( scanner.hasNext() )
    {
        String studentName = scanner.nextLine();
        while(i < 3)
        {
            try
            {
                marks[i] = scanner.nextInt();
                i++;
            }
            catch ( InputMismatchException ex )
            {
                i=0;
            }
        }
        scanner.nextLine();
        storeStudentRecord(studentName, marks);
        //scanner.nextLine();
        i=0;
    }
    scanner.close();
}

Code for storing values in another class

    private void storeStudentRecord(String name, int[] marks)
{
    //int[] x = new int[3]
    StudentRecord student = new StudentRecord(name, marks);
    marksList.add(student);
}

Constructor method in other class

    public StudentRecord(String nameInput, int[] marksInput)
{
    // initialise instance variables
    name = nameInput;
    noOfMarks = 0;
    marks = marksInput;
}

This has been driving me nuts for hours so any help would be greatly greatly appreciated, thank you.

You're reusing the same array. Don't. Java passes references so you end up with an `ArrayList` where each element point to the same memory location. — Boris the Spider, Feb 15 '17 at 17:17
Try moving the line `int[] marks = new int[3];` inside the outer `while` loop — Pravin Sonawane, Feb 15 '17 at 17:19
[What does your step debugger tell you?](http://stackoverflow.com/questions/25385173/what-is-a-debugger-and-how-can-it-help-me-diagnose-problems) — , Feb 15 '17 at 17:25
@JarrodRoberson not sure that's the intended use of the duplication function. — Boris the Spider, Feb 15 '17 at 17:27

boxed__l · Answer 1 · 2017-02-15T17:23:13.320

0

You could modify the constructor so that it creates a copy of the array and uses it :

public StudentRecord(String nameInput, int[] marksInput)
{
    // initialise instance variables
    name = nameInput;
    noOfMarks = 0;
    if(marksInput!=null)
     marks = Arrays.copyOf(marksInput, marksInput.length);
    else
     marks = null;
}

edited Feb 15 '17 at 17:23

answered Feb 15 '17 at 17:21

boxed__l

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Contents of array being overwritten

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