Changing the attribute of an instance object of a class that's declared in another pa

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February 14th, 2013, 05:36 PM

wholegrain

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Changing the attribute of an instance object of a class that's declared in another pa

Ok, so I have a bunch of classes and I'd like to rotate an object which has an object shape, which is a 2d array and that's constructed in the parent class of the object class. I want to change the attribute (shape) in the method rotate() which calls the method multiplyarray that does the rotation by changing the shape. However, I realized that I don't have access to shape, or at least I don't know how to change it. I don't think the parent class has a public setShape method. Anyway here's the code:

Code:

public static int[][] multiplyMatrix(int[][] m1) {

    int[][] m2 = { { 0, 0, 0, 1 }, { 0, 0, 1, 0 }, { 0, 1, 0, 0 },
            { 1, 0, 0, 0 }, };

    int[][] result = new int[4][4];

    // multiply
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < 4; j++)
            for (int k = 0; k < 4; k++)
                if (m1[i][k] * m2[k][j] > 0) {
                    result[i][j] = 1;
                } else {
                    result[i][j] = 0;
                }

    return result;
}

the rotate method:

Code:

synchronized void rotateClockwise() {
    currentPiece.shape = multiplyMatrix(shape);

    //gives me an error
    updateLocation();
}

the constructor (all three methods are in the same class):

Code:

    public Piece(int shape[][]) {
    super(shape);
    currentX = 7;
    currentY = 2;
    updateLocation();
}

this method is in another class and it contains the instance object whose attribute i want to modify:

Code:

public void keyPressed(KeyEvent event) {
    int key = event.getKeyCode();
    switch (key) {
    case KeyEvent.VK_UP: // up arrow
    case KeyEvent.VK_KP_UP:
        currentPiece.rotateCounterclockwise();
        break;
    case KeyEvent.VK_DOWN: // down arrow
    case KeyEvent.VK_KP_DOWN:
        currentPiece.rotateClockwise();
        break;
    case KeyEvent.VK_LEFT: // left arrow
    case KeyEvent.VK_KP_LEFT:
        currentPiece.moveLeft();
        break;
    case KeyEvent.VK_RIGHT: // right arrow
    case KeyEvent.VK_KP_RIGHT:
        currentPiece.moveRight();
        break;
    case KeyEvent.VK_SPACE: //  space bar
        currentPiece.drop();
    }
}

createPiece method (I want to access the shape attribute):

Code:

public static Piece createPiece() {
    int[][] s = SHAPES[(int) (Math.random() * SHAPES.length)];
    switch ((int) (Math.random() * 10)) {
    case 0:
    case 1:
    case 2:
    case 3:
    default:
        return new Piece(s);
    }
}

entire code can be found here (without certain modifications):

http://mathcs.slu.edu/~fritts/cse131/labs/lab9/index.html

Update:

I found out that super calls this constructor in Grid:

Code:

public Grid(int[][] contents) {
    this.contents = contents;
    Dimension d = new Dimension(getColumns()*Tetris.SQUARE_SIZE,
                                getRows()*Tetris.SQUARE_SIZE);
    setSize(d);
    setPreferredSize(d);
    setOpaque(false);
}

Now, I tried this:

Code:

synchronized void rotateClockwise() {
Grid.contents = multiplyMatrix(Grid.contents);
updateLocation();

}

It gives me:

non-static method getContents() cannot be referenced from a static context

February 15th, 2013, 06:13 AM

NormR

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Join Date: Aug 2010

Location: SW Missouri

Posts: 3,048

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Also posted at http://www.javaprogrammingforums.com/whats-wrong-my-code/23845-changing-attribute-instance-object-class-thats-declared-another-package-whose-variable-constructed-its-parent-class.html