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Thread: Problem with array values

  1. #1
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    Default Problem with array values

    I'm trying to get java to draw 100 squares in a grid but it's not working properly. It compiles and runs without error but it only prints 1 square. Uncommenting the println() in makeGrid() shows the array is filled with the right values but the println() in paint() shows every entry is exactly the same (the last entry entered is repeated)
    I have no idea how the values are changed or why.

    import java.awt.*;
    import java.awt.event.*;
     
    public class GridTest extends Canvas
    {
        private int squaresize;
        private int[] grid = new int[100];
        private Rectangle[] rects = new Rectangle[100];
        private int offset = 25;
     
        public Dimension getPreferredSize() {
            return new Dimension(300,300);
        }
     
        public void makeGrid()
        {
            squaresize = 10;
            for(int h=0;h<100;h++)
            {
                grid[h] = h;
                for(int i=0;i<10;i++)
                {
                    for(int j=0;j<100;j+=10)
                    {
                        this.rects[h] = new Rectangle(offset + j, offset + (i*10), squaresize, squaresize);                    
                        //System.out.println(rects[h].toString());
                    }
                }
            }
        }
     
        public void paint(Graphics g)
        {
            Graphics2D g2 = (Graphics2D) g;
            g2.setColor(Color.BLACK);        
            for(int i=0;i<rects.length;i++)
            {
                g2.draw(rects[i]);
                //System.out.println(rects[i].toString());
            }
        }
     
        public static void main(String[] args)
        {
            GridTest gt = new GridTest();
            gt.makeGrid();
            Frame f = new Frame("GridTestFrame");
            f.addWindowListener(new WindowAdapter() {
                public void windowClosing(WindowEvent e) {
                    System.exit(0);
                }
            });
            f.add(gt);
            f.pack();
            f.setVisible(true);
        }
    }
    Last edited by Harry Blargle; September 17th, 2011 at 05:05 PM.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Problem with array values

    Did you look at the 100 lines of print outs?
    Did it look like there were different rectangles?
    What was the difference between one rectange and the next one?

  3. #3
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    Default Re: Problem with array values

    Yes, like i said, the first println shows the proper x and y values on everything, the second one shows the same x and y value for everything (115)

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Problem with array values

    Which is the first println? The one in makeGrid? How many lines does it print? Add a separate counter variable and print that with the rects value:
    System.out.println("cntr=" + cntr++ + " " +rects[h].toString() + ", h=" + h);
    Define cntr as an int outside of the loops.

    The second println in the paint method shows that the contents of the array are all the same.
    Look at how the index to the array changes as you are creating the elements and storing them in the array.
    Last edited by Norm; September 17th, 2011 at 04:29 PM.

  5. #5
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    Default Re: Problem with array values

    i changed it to:
    int h = 0;
    for(int i=0;i<10;i++)
    {
            for(int j=0;j<100;j+=10)
            {
                    rects[h] = new Rectangle(offset + j, offset + (i*10), squaresize, squaresize);
                    h++;
            }
    }

    now it works! thanks for the help Norm

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: Problem with array values

    Yep. That looks like it'd work.

  7. The Following User Says Thank You to Norm For This Useful Post:

    Harry Blargle (September 17th, 2011)

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