Question

Using java :

In this exercise, you need to implement a class that encapsulate a Grid. A grid is a useful concept in creating board-game applications. Later we will use this class to create a board game. A grid is a two-dimensional matrix (see example below) with the same number of rows and columns. You can create a grid of size 8, for example, it’s an 8x8 grid. There are 64 cells in this grid. A cell in the grid can have any arbitrary value. Later in this course, we will learn how to create a cell that can hold any arbitrary values. However, for the time being, we will assume that the cell-values are non-negative integers. If a cell contains a value ‘0’ that means, the cell is empty. To identify a cell, you need row number and column number, for example, cell (1, 3) means 3rd cell of the 1st row. You need to create a class that satisfies the following requirements.

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1 2 3 4 5 6 7 7 6 5 4 3 2 Each box is a "cell"

Tasks Write tests and code for each of the following requirements, in order. The words in bold indicate message names. Whenever a requirement says the user can "ask whether...", the expected answer is boolean. Whenever a requirement speaks of a "particular" item, then that item will be an argument to the method. 1. The user can create a Grid specifying the number of row and column. Also the user can create a Grid specifying the size only.

2. The user can ask a Grid whether its isEmpty. A grid is empty when all the cells of the grid is empty.

3. The user can clear all the cells of the grid. It’s a void method.

4. The user can ask a Grid whether a particular cell isValid. Each box is a “cell”

5. The user can ask a Grid to set a particular value by setValue to a particular row and col. The grid sets the value only if that cell is valid.

6. The user can ask a Grid to getValue (in this case integer) from a particular row and col. The grid returns the value only if the locations are valid.

7. The user can ask a Grid to set part of its row and column with particular values. Example, setCells(int rows[], int cols[], int vals[]), in this method user can specify the indexes of rows and columns that the user wants to set with some particular values (supplied in vals array). Note that, rows, cols, and vals arrays should be of same size.

8. Make another overridden method for setCells(int rows[], int cols[], int v), that will set particular rows and cols of a grid with a particular value.

Apart from these basic requirements, feel free to add more behaviors to the Grid class that you think appropriate. Please provide an explanation for those behaviors as a comment in the source file.

Write a test class to test the behaviors of the Grid class and submit the test class as well.

Note: A grid is composed of many cells. So, you may want to decompose the grid into a Cell class that encapsulates all the necessary behavior of a cell in the grid

Answer 1

// Grid.java
public class Grid {
    private int row, col;

    // Note: we have taken Integer(wrapper) not integer(primitive) type
    // so that empty cells have default value as null
    private Integer data[][];

    // constructors
    public Grid(int size) {
        row = col = size;
        data = new Integer[size][size];
    }

    public Grid(int row, int col) {
        this.row = row;
        this.col = row;
        data = new Integer[row][col];
    }

    // check if all cells are empty
    public boolean isEmpty() {
        for(Integer[] r: data) {
            for(Integer v: r) {
                if(v != null) {
                    return false;
                }
            }
        }
        return true;

 }

    public void clear() {
        data = new Integer[row][col];
    }

    public boolean isValid(int r, int c) {
        if(r < 0 || r >= row || c < 0 || c >= col) {
            return false;
        } else {
            return true;
        }
    }

    public void setValue(int r, int c, Integer value) {
        if(isValid(r, c)) {
            data[r][c] = value;
        }
    }
    public Integer setValue(int r, int c) {
        if(isValid(r, c)) {
            return data[r][c];
        } else {
            return null;
        }
    }

    public void setCells(int r[], int c[], int values[]) {
        if(r.length == c.length && r.length == values.length) {
            int len = r.length;

            for(int i=0; i<len; i++) {
                if(isValid(r[i], c[i])) {

data[r[i]][c[i]] = value;
                }
            }
        }
    }

    public void printGrid() {
        System.out.println();
        for(Integer r[]: data) {
            for(Integer v: r) {
                System.out.printf("%3s", (v==null?"-":v));
            }
            System.out.println();
        }
    }

    public static void main(String args[]) {
        Grid g = new Grid(5);
        System.out.println(g.isEmpty());

  g.printGrid();

        g.setCells(new int[]{1, 2, 3}, new int[]{1, 2, 3}, new int[]{1, 2, 3});

        g.printGrid();
    }
}

Grid.java 75 } } 76 77 public void printGrid () 78e System.out.println(); for(Integer r[]: data) for(Integer System.out.printf ( "%3s ", (v==null?"-":v)); } System.out.println (); 79 80 81 v: 82 83 84 85 } 86 87 88e 89 90 91 92 93 94 95 96 97 public static void main(String args[]) { Grid g new Grid(5); System.out.println(g.isEmpty ()) g.printGrid() g.setCells(new int[]1, 2, 3}, int []{1, 2, 3} int[]{1, 2, 3}); new new g.printGrid(); } 98 99 Console 3 <terminated> Grid [Java Application] C:\Program Files\Java\jdk1.8.0_60\bin\javaw.exe (Feb 25, 2018, 2:42:01 AM) true 2

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