The code below creates 3 3x3 boxes of "." and adds an ant ("A") in a random location. You can run the code and realize what I mean.

I want to be able to, in Java, 1) make sure the space is null and generate a random direction in the grid array, 2) let Ant move to a random direction using the move method and 3) finish the move method in Doodlebug with the same behavior.

For example, to go up in the grid, it would say grid [ant.x-1] [ant.y]

down: grid [ant.x+1] [ant.y]

left: grid [ant.x] [ant.y-1]

right: grid [ant.x] [ant.y+1]

Also, I wasn't sure how to post the code, it came out in a weird table, I apologize.

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abstract public class Critter {
	protected World myWorld; // know in which world the critter lives
	protected int x, y; // Position in the world
	abstract public void move();
	public Critter(World world, int rIndex, int cIndex){
	myWorld = world;
	x = rIndex;
	y = cIndex;
	}
	public abstract void display();
	}

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import java.util.Random;
	public class Ant extends Critter {
	public Ant(World world, int rIndex, int cIndex) {
	super(world, rIndex, cIndex);
	}
	public void move(){
	//System.out.println("ant move");
	//todo:
	// Check whether the cell below is available
	//
	// If the cell below is available
	//(the cell is not out of boundary and is empty),
	// put the ant to the next cell
	// Else: the ant does not move
	int gridsize = this.myWorld.getGridSize();
	int newx = this.x+1;
	if(newx >= gridsize)
	{ return;
	}
	Critter cell = this.myWorld.getCell(this.x+1,this.y);
	if( cell == null)
	this.myWorld.setCell(this.x+1, this.y, this);
	this.myWorld.setCell(this.x, this.y, null);
	}
	public void display()
	{
	System.out.print('A');
	}
	//if idex is (i, j) -- to get to the cell below it (i +1, j)
	}

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public class Doodlebug extends Critter {

public Doodlebug(World world, int rIndex, int cIndex) {

super(world, rIndex, cIndex);

}

public void move(){

//System.out.println("doodlebug move");

}

@Override

public void display()

{

System.out.print('D');

}

}

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public class Main {
	public static void main(String[] argv){
	World world = new World(3);
	world.AssignCritters(4, 1);
	world.Display();
	System.out.println(" ");
	world.oneStepSimulation();
	world.Display();
	}
	}

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import java.util.Random;
	public class World {
	private Critter[][] grid; // Array of organisms for each getCell
	public Critter getCell(int i, int j){
	return grid[i][j];
	}
	public void setCell(int x, int y, Critter c) {
	this.grid[x][y] = c;
	}
	public int getGridSize(){
	return grid.length;}
	public World(int gridsize){
	grid = new Critter[gridsize][gridsize];
	for(int i = 0; i < gridsize; i++){
	for(int j = 0; j < gridsize; j++){
	grid[i][j] = null;
	}
	}
	}
	public void Display(){
	for (int i=0; i < grid.length; i++)
	{
	for (int m = 0; m < grid.length; m++)
	{
	if (grid [i] [m] == null)
	System.out.print(" .");
	else
	{ grid [i] [m].display();
	}
	}
	System.out.print(" ");
	}
	}
	public static void main(String[] argv){
	World world = new World(5);
	world.AssignCritters(10, 15);
	world.Display();
	}
	public void oneStepSimulation(){
	for (int i = 0; i < grid.length; i++){
	for (int j = 0; j < grid.length; j++){
	if (grid[i][j]!=null){
	grid[i][j].move();
	}
	}
	}
	}
	public void AssignCritters(int antNumber, int critterNumber)
	{
	Random r = new Random();
	int rIndex = r.nextInt(grid.length);
	int cIndex = r.nextInt(grid[rIndex].length);
	for (int i=0; i < antNumber; i++)
	if ( grid [rIndex] [cIndex] == null) {
	grid[rIndex] [cIndex] = new Ant(World.this, rIndex, cIndex); }
	// else { Ant.move();
	//}
	}
	}