Cafe Wall Illusion

Question

Here is the expected output of my code:

And here is my code:

import java.awt.*;

public class CafeWall
{
    final static int MORTAR = 2;
    final static int WIDTH  = 650;
    final static int HEIGHT = 400;

    public static void main( String[] args )
    {
        StdDraw.setCanvasSize(WIDTH, HEIGHT);
        StdDraw.setXscale(0, WIDTH);
        StdDraw.setYscale(0, HEIGHT);

 // Change from Color.GRAY to change background color.
        StdDraw.setPenColor( Color.GRAY );
        StdDraw.filledRectangle(WIDTH/2, HEIGHT/2, WIDTH/2, HEIGHT/2);

 drawRow(    0, 378, 4, 20 );
 drawRow(   50, 300, 5, 30 );

 drawGrid(  10, 36, 4, 25, 0 );

 drawGrid( 250, 40,  3, 25, 10 );

 drawGrid( 425, 2, 5, 20, 10 );

 drawGrid( 400, 234,  2, 35, 35 );
    }

    // Draw a row of squares, the total number of squares is pairs * 2
    // (x, y) is the lower left corner of the first box
    public static void drawRow( int x, int y, int pairs, int size )
    {
      StdDraw.setPenColor(Color.BLACK);
      StdDraw.filledRectangle(x, y, size, size);
      StdDraw.setPenColor(Color.BLUE);
      StdDraw.line(x, y, x+size, y+size);
      StdDraw.line(x, y+size, x+size, y);
      StdDraw.setPenColor(Color.WHITE);
      StdDraw.filledRectangle(x+size, y, size, size);
    }

    // Draw a grid of 2 * pairs rows
    public static void drawGrid( int x, int y, int pairs, int size, 
     int offset )
    {
      int startingX = x;
      for(int line = 1; line <= pairs; line++) {
        if(line % 2 ==1) { //if line is odd
          x = startingX;
        } else { //else line is even and must be shifted by offset specified
          x = startingX + offset;
        }
        for(int i = 1; i <= pairs; i++) {
          drawRow(x, y, pairs, size);
          x = x + 2*size;
        }

        y = y + size + MORTAR;
      }
    }


}

Problems:

• My rows are not offset properly
• my blue "x's" are not showing up.

I have been staring at this for hours. I cannot seem to figure out where I have gone wrong. Can anyone offer some guidance?

---

(Additional note) This is the actual output of this code for those who are wondering:

Answer 1

There are two significant issues you have with your drawRow():

1. You are not centering the rectangles in the drawRow correctly
2. you are not repeating the pairs correctly in the drawRow

This is what that method should look like:

public static void drawRow( int x, int y, int pairs, int size ) {
    // loop for each pair.
    for (int i = 0; i < pairs; i++) {
        StdDraw.setPenColor(Color.BLACK);
        // Note the correct centering of the rectangles
        StdDraw.filledRectangle(x + size/2, y + size/2, size / 2, size/2);
        StdDraw.setPenColor(Color.BLUE);
        StdDraw.line(x, y, x+size, y+size);
        StdDraw.line(x, y+size, x+size, y);
        StdDraw.setPenColor(Color.WHITE);
        // Note the correct centering of the rectangles
        StdDraw.filledRectangle(x+size+size/2, y + size/2, size / 2, size/2);
        // advance to the next pair.
        x += size * 2;
    }
}

in your drawGrid() method you should have an additional rows parameter which indicates how many rows to draw. I have modified that method to look like:

public static void drawGrid( int x, int y, int rows, int pairs, int size, 
        int offset )
{
    int startingX = x;
    for(int line = 0; line < rows; line++) {
        x = startingX + (line % 2) * offset;
        drawRow(x, y, pairs, size);

        y = y + size + MORTAR;
    }
}

Note the 'clever' use of the (line % 2) * offset. Figure that one out.

Putting it together, and changing the size of some of the rows, I have the main method calls:

    drawRow(    0, 378, 4, 20 );
    drawRow(   50, 300, 5, 30 );

    // Bottom left
    drawGrid(  10, 36, 4, 4, 20, 0 );

    // bottom mid
    drawGrid( 250, 40, 6, 3, 25, 10 );

    // bottom right
    drawGrid( 425, 2, 10, 5, 16, 8 );

    // top right
    drawGrid( 400, 234, 4, 2, 35, 35 );

and my result looks like:

These are not huge changes from what you had... just a little bit of logic here and there.