Thread: Changing the attribute of an instance object of a class that's declared in another package and whose variable is constructed by its parent class

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:

HTML 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:

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

    //gives me an error

    updateLocation();

}

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

HTML 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:

HTML 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):

HTML 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);
    		}

I found out that super calls this constructor in Grid:

HTML 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:

HTML Code:

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

}

It gives me:

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


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

CSE131 Lab 9: Tetris Game using Object-Oriented Design

Can you tell me how to make my rotation method worki?

Like I don't even know what variable to modify.

--- Update ---

Basically, I am trying to make a tetris game, and I am basically multiplying the shape object with another vector to make it rotate.

Tetris Piece Rotation Algorithm - Stack Overflow

However, I can't seem to modify the block as they fall down by rotating them with the push of a key. I can move them left and right, but I can't rotate them.

I don't even know what I am doing. Don't assume I know what I am doing. I suspect the entire logic is wrong. I'll try to post the error as soon as I can.

--- Update ---

void static updateLocation() {
setLocation(Tetris.SQUARE_SIZE*currentX,
(int) (Tetris.SQUARE_SIZE*currentY));
}

I changed rotateClockwise to static and it gave me new errors. They weren't there before... Do you want me to post the entire source?

error: <identifier> expected
error: '(' expected
error: invalid method declaration; return type required

Basically, there is an enum array object with 1 and 0 passed into the constructor for the class Piece randomly, and it calls super(shape), which creates a Grid object. The currentPiece, which I think is the variable I need to modify is created in the main class and I can't access it even though it's an object of type Piece, and since the object has a parameter shape, I can't pass the object currentPiece directly in my matrixMultiplication object. So I don't know what to do. I tried currentPiece.shape, but it didn't work. It's an instance of the object Piece, so it's supposed to work, but it doesn't...

--- Update ---

Originally Posted by Norm

What lines does each error message go with?


You should not use static on anything except the main() method.

line 26, which is the first line of the three

full source code:

public class Piece extends Grid {
	int currentX;     // current X location on  the board
	double currentY;  // current Y location on the board
 
 
	public Piece(int shape[][]) {
		super(shape);
		currentX = 7;
		currentY = 2;
		updateLocation();
	}
 
 
	void updateSize() {
		setSize(Tetris.SQUARE_SIZE*getColumns(),
				Tetris.SQUARE_SIZE*getRows());
	}
 
	void static updateLocation() {
		setLocation(Tetris.SQUARE_SIZE*currentX,
					(int) (Tetris.SQUARE_SIZE*currentY));
	}
 
	synchronized void moveDown() {
 
	}
 
	synchronized void moveLeft() {
		currentX--;
		updateLocation();
	}
 
	synchronized void moveRight() {
		currentX++;
		updateLocation();
	}
 
    synchronized static void rotateClockwise() {
    	Grid.contents = multiplyMatrix(Grid.contents);
		updateLocation();
 
	}
 
	synchronized void rotateCounterclockwise() {
	}
 
	void fall() {
		// replace the following by your code
		Tetris.sleep(2000);
	}
 
	synchronized void drop() {
		currentY++;
		updateLocation();
	}
 
  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;
  }
 
    }

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
public class Tetris extends JFrame implements KeyListener {
	public static final int SQUARE_SIZE = 10; // 10 by 10 pixels
 
	static Board board;
	static Tetris game;
 
	JPanel mainPanel;
	public Piece currentPiece;
	int score = 0;
	JButton scoreButton;
 
	public Tetris() {
		super("Tetris");
		game = this;
		Container pane = getContentPane();
		pane.setLayout(new BorderLayout());
 
		scoreButton = new JButton("0");
		scoreButton.setEnabled(false);
		pane.add(scoreButton,BorderLayout.NORTH);
 
		board = new Board();
		mainPanel = new JPanel();
		mainPanel.setLayout(null);
		mainPanel.add(board);
		mainPanel.setPreferredSize
			(new Dimension(Board.COLUMNS*SQUARE_SIZE,
						   Board.ROWS*SQUARE_SIZE));
		pane.add(mainPanel);
 
		addKeyListener(this);
		addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent we) {
				System.exit(0);
			}
		});
		pack();
		show();
		setResizable(false);
	}
 
 
	public void addToScore(int v) {
		score += v;
		scoreButton.setText(""+score);
	}
 
	public int getScore() {
		return score;
	}
 
	static Board getBoard() {
		return board;
	}
 
	static Tetris getGame() {
		return game;
	}
 
	static void sleep(int milliseconds) {
		try {
			Thread.sleep(milliseconds);
		} catch (InterruptedException ie) {
		}
	}
 
	public static void main(String[] args) {
		Tetris game = new Tetris();
		while (true) {
			game.dropPiece();
		}
	}
 
	void dropPiece() {
		currentPiece = PieceFactory.createPiece();
		mainPanel.add(currentPiece);
		currentPiece.repaint();
		currentPiece.fall();
		//mainPanel.remove(currentPiece);
		board.repaint();
		addToScore(1);
	}
 
	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();
		}
	}
 
	public void keyReleased(KeyEvent arg0) {
	}
 
	public void keyTyped(KeyEvent arg0) {
	}
 
 
}

import javax.swing.JComponent;
import java.awt.*;
 
public class Grid extends JComponent {
	public int contents[][];  // each rows is an array of integers
 
	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);
	}
 
	public int[][] getContents()
	{
		return contents;
	}
 
	public int getColumns() {
		return contents[0].length;
	}
 
	public int getRows() {
		return contents.length;
	}
 
	void paintSquare(int row, int col, Graphics g) {
		if (contents[row][col] != 0)
			g.fillRect(Tetris.SQUARE_SIZE*col+1,
						Tetris.SQUARE_SIZE*row+1,
						Tetris.SQUARE_SIZE-2,
						Tetris.SQUARE_SIZE-2);
	}
 
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		for (int row = 0; row < contents.length; row++) {
			for (int col = 0; col < contents[row].length; col++) {
					paintSquare(row,col,g);
			}
		}
	}
}

public class PieceFactory {
 
	public static final int[][] L1 =
		{{1,1,0,0},
		 {0,1,0,0},
		 {0,1,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][] L2 =
		{{0,1,0,0},
		 {0,1,0,0},
		 {1,1,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][] T =
		{{0,1,0,0},
		 {1,1,0,0},
		 {0,1,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][] BOX =
		{{1,1,0,0},
		 {1,1,0,0},
		 {0,0,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][] BAR =
		{{1,1,1,1},
		 {0,0,0,0},
		 {0,0,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][] STEP1 =
		{{1,0,0,0},
		 {1,1,0,0},
		 {0,1,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][] STEP2 =
		{{0,1,0,0},
		 {1,1,0,0},
		 {1,0,0,0},
		 {0,0,0,0},
		};
 
	public static final int[][][] SHAPES = {L1,L2,T,BOX,BAR,STEP1,STEP2};
 
	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);
		}
 
 
	}
 
 
 
 
}

import java.awt.*;
 
public class Board extends Grid {
	public static final int COLUMNS = 16;
	public static final int ROWS = 32;
	public static final Color BLUE = new Color(0,0,128,40);
 
	public Board() {
		super(new int[ROWS][COLUMNS]);
		setSize(COLUMNS*Tetris.SQUARE_SIZE,
				ROWS*Tetris.SQUARE_SIZE);
	}
 
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		g.setColor(BLUE);
		paintStripes(g);
	}
 
	void paintStripes(Graphics g) {
		for (int i = 0; i < COLUMNS; i += 4) {
			g.fillRect(i*Tetris.SQUARE_SIZE,0,
				Tetris.SQUARE_SIZE*2,Tetris.SQUARE_SIZE*ROWS);
		}
	}
 
 
}

--- Update ---

me neither, but I think it's because my rotate object shouldn't be static, because the errors disappear when I remove static.

But it doesn't work.

It's supposed to multiply matrix a with another matrix that will "rotate" matrix a and return it to another variable, which will be assigned to the shape of currentPiece. I don't know how to do the last part. I tried various things, but they don't work or sometimes don't even compile.

I am trying to do a matrix multiplication with 1 and 0 as values.

Binary Matrix Multiplication & Boolean Product

It doesn't have a setShape() method, but the constructor calls super(shape) and it seem that the constructor in Grid does something with shape, so I don't think if that would make it work.

I just added this in the Piece class:

public void setShape(int shape[][])
{
this.shape = shape;
}

when I compile, I get this:
error: cannot find symbol

Originally Posted by Norm

when you post error messages, you need to copy all of the message.
What you posted does not give the symbol that is not found or the source line with the error. You need that information to solve the problem.

I'm done for tonight. Back tomorrow.

it's shape

--- Update ---

Ok, I need to do the following and I don't know how to do them:

Change currentPiece and access the shape of the currentPiece, which is created in Tetris.java.

Someone please help me.

Originally Posted by Norm

Where is the variable shape defined in the Tetris class?


Also posted at Changing the attribute of an instance object of a class that's declared in another pa - Dev Shed

Shape is an attribute of Piece and is constructed in Grid as contents. Can you look at the source and tell me how to do it?

How can you ask me to write a program that compiles and that shows the problem? If I could do that, I wouldn't even be asking for help. I told you the problem was that I can't change shape, which seems to be an attribute of Piece and that's constructed using super() and that is passed to the constructor in Grid as contents. Now, I would like to write a method in Piece that changes its instance currentPiece so I can rotate its shape, but I don't know how to do that. So my question is: what can I change in the program to get the access right needed to change shape in the instance currentObject.

Ok, shape is an int[][]

the shape variable is passed in as an argument in the class PieceFactory (it is randomly generated through Math.Random which picks a shape enum object from a given list)

the constructor in Piece calls super(shape), and that shape goes to the constructor in Grid.

Now, I thought of doing the following and I would like to help me find a way to implement it or tell me there's a better way or whatever:

Since the constructor in Grid seem to do something important, I think I need to create a new constructor that has currentX, currentY and shape as an argument. However, I need to access shape from currentPiece.shape (which is a Piece object initialized in Tetris.java), but I can't do that. Moreover, Tetris calls currentPiece.rotateCounterClockwise. Strangely, it's supposed to use currentPiece, but I don't know how exactly. Isn't it better to call currentPiece as an argument? Should I change that? Also, changing Grid.shape serves no purpose as currentPiece won't be affected. Now, the first thing I need to achieve is to be able to pass currentPiece.shape into the MatrixMultiplication method. Can you tell me how I might be able to do that?