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Racer (Part 5/28)

Games, Level 0, Lesson 5

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I'm confused as to why they are using these values as well this.width = matrix[0].length; this.height = matrix.length;

Create a GameObject class to represent game objects. All game objects will have the following common properties:

- int x, int y — coordinates of the object's upper left corner on the playing field;
- int[][] matrix — matrix for displaying the game object. The matrix values are the ordinals of the colors in the Color enum.

To get the color, use Color.values()[matrix[i][j]], where:

i is the y coordinate in the matrix,
j is the x coordinate in the matrix.

- int height, int width — The height and width match the dimensions of the matrix.

An object must also have a method that draws it.

Requirements:

There must be a public GameObject class in a separate file.
The GameObject class must have a public int x field.
The GameObject class must have a public int y field.
The GameObject class must have a public int[][] matrix field.
The GameObject class must have a public int width field.
The GameObject class must have a public int height field.
The GameObject class must have a public constructor with three parameters (int, int, int[][]). It must use the parameters to set the x and y fields and the matrix field.
In the GameObject's constructor, the width field must be initialized to the value matrix[0].length, where matrix is the constructor's last parameter.
In the GameObject's constructor, the height field must be initialized to the value matrix.length, where matrix is the constructor's last parameter.
The GameObject class must have a public void draw(Game) method.
The draw(Game) method must call the setCellColor(int, int, Color) method on the Game object for each cell of the matrix. The following arguments must be passed: the object's x + x in the matrix, the object's y + y in the matrix, color.
The GameObject class must have a statement that imports the entire contents of the com.codegym.engine.cell package.

package com.codegym.games.racer; // import com.javarush.engine.cell.*; import com.codegym.engine.cell.Color; import com.codegym.engine.cell.Game; public class RacerGame extends Game { public static final int WIDTH = 64; public static final int HEIGHT = 64; public static final int CENTER_X = WIDTH / 2; public static final int ROADSIDE_WIDTH = 14; public void initialize() { showGrid(false); setScreenSize(WIDTH, HEIGHT); createGame(); } private void createGame() { drawScene(); } private void drawScene() { drawField(); } private void drawField() { for (int x = 0; x < HEIGHT; x++) { // create three conditionals for (int y = 0; y < WIDTH; y++) { if (x == CENTER_X) { setCellColor(x, y, Color.WHITE); } else if (x >= ROADSIDE_WIDTH && x < (WIDTH - ROADSIDE_WIDTH)) { setCellColor(x, y, Color.DIMGREY); } else { setCellColor(x, y, Color.GREEN); } } } } public void setCellColor(int x, int y, Color color) { // super(x, y, color); try { super.setCellColor(x, y, color); if ((x > 64 || x < 0) || (y > 64 || y < 0)) { throw new Exception(); } } catch (Exception e) { System.out.println("x and y values are out of bounds"); e.printStackTrace(); } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

1 September 2021, 14:40

It looks like the draw method is drawing objects on the view screen in the wrong location. Take, for example, a 2x2 matrix. If it we were to start drawing it on the screen at a random location, lets say starting at (x:5, y:7). That means the picture should be drawn on the coordinates: (5,7) (6, 7) (5,8) (6,8) If you take the above code and apply it to this scenario the x loop (line 25) would start x at 5, and the y loop (line 27) would start y at 7. This is correct. However, going to line 29: game.setCellColor(this.x + x, this.y + y, Color.values()[matrix[y][x]]); Problems occur. This code would place the first "pixel" at this.x + x and this.y + y, which if x and y start at 5 and 7 respectively and then you add 5 and 7 to them, the pixel would be drawn at (10, 14) instead of (5,7). Continuing that the full placement of the object on screen would be at: (10,14) (12,14) (10,16) (12,16) This would create a disconnected object on screen and most likely would crash your code with an index out of bounds exception whenever an object is past the half way mark of the max x or max y.

Guadalupe Gagnon

Level 37 , Tampa, United States

1 September 2021, 14:56

"I'm confused as to why they are using these values as well this.width = matrix[0].length; this.height = matrix.length;" A multidimensional array, such as matrix, is an array which has sub arrays in its indices. So a 2x2 matrix would be declared like this int[2][2], and look something like this: [ [0, 1], [2, 3] ] So the first index (index 0) contains the array [0,1] and the second index contains the array [2,3] See in example code:

int[][] temp = {{0,1},{2,3}};
System.out.println("temp[0]: " + Arrays.toString(temp[0]));
System.out.println("temp[1]: " + Arrays.toString(temp[1]));

So if you take the first index of a two dimensional array, such as matrix, you are going to get the very first sub array. The length of that sub array, when considering the whole matrix as a picture, is going to its width. The length of matrix, or how many sub arrays it has, will be considered its height. For example, if we had a matrix[4][5], it would look something like this:

// 1  2  3  4  5 ←the width
  [0, 0, 0, 0, 0] // 1
  [0, 0, 0, 0, 0] // 2
  [0, 0, 0, 0, 0] // 3
  [0, 0, 0, 0, 0] // 4
//                   ↑ the height

And an example of this in code:

int[][] temp = new int[4][5];
System.out.println(" 1  2  3  4  5");
int j = 1;
for(int[] x : temp) System.out.println(Arrays.toString(x) + " ← " + j++);
System.out.println("width: " + temp[0].length);
System.out.println("height: " + temp.length);