Question

        this.size = 9;
        this.populationSize = 10;
        Random rand = new Random();


        Integer[][] easy1 = new Integer[size][size];
        easy1 = this.initializeEasy1(easy1);
        this.sudokuArray = new Sudoku[this.populationSize];
        for (int i = 0; i < this.sudokuArray.length; i++){
            long seed = rand.nextLong();
            System.out.println("" + seed);
            this.sudokuArray[i] = new Sudoku(easy1, this.size, seed);
        }

I am building an evolutionary sudoku solver and I am having a problem where the last Sudoku object is overwriting all the other objects in the array. Where in the code did I mess up?

/edit here is the constructor of the class

public Sudoku(Integer[][] givensGrid, int s, long seed){
    this.size = s;
    this.givens = givensGrid;
    this.grid = this.givens.clone();
    Random rand = new Random(seed);

    System.out.println("Random " + rand.nextInt());
    // step though each row of the grid
    for (int i = 0; i < size; i++){
        ArrayList<Integer> numbers = new ArrayList<Integer>();
        numbers = this.makeNumbers(numbers);

        // step through each column to find the givens and remove from numbers
        for (int j = 0; j < size; j++){
            if (this.grid[i][j] != 0){
                numbers.remove(this.grid[i][j]);
            }
        }
        // go back through the row and assign the numbers randomly
        for (int j = 0; j < size; j++){
            if (this.grid[i][j] == 0){
                int r = rand.nextInt(numbers.size());
                this.grid[i][j] = numbers.get(r);
                numbers.remove(r);
            }
        }
    }
    System.out.println("=============");
    System.out.println(this.toString());
}

here is the fixed code

this.size = 9;
    this.populationSize = 10;
    Random rand = new Random();


    Integer[][] easy1 = new Integer[size][size];
    this.sudokuArray = new Sudoku[this.populationSize];
    for (int i = 0; i < this.sudokuArray.length; i++){
        long seed = rand.nextLong();
        easy1 = new Integer[size][size];
        easy1 = this.initializeEasy1(easy1);
        System.out.println("" + seed);
        this.sudokuArray[i] = new Sudoku(easy1, this.size, seed);
    }

Answer 1

When you declare easy1 to be a new Integer 2D array, you are saying that easy1 is a reference to 1 2D array object.

You are then adding a new Sudoku object which references the same 2D array, since you are passing the reference to it. Thus, all of your sudoku objects are referencing just 1 2D array, which is probably not what you want.

I would rather change this line to:

this.sudokuArray[i] = new Sudoku(new Integer[size][size], size, seed);

Does that make sense?