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Thread: Respawn moving objects on 2D array

  1. #1
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    Default Respawn moving objects on 2D array

    I have a 2D array grid on which a couple of runnable vehicle objects (an 'x' and an 'o') are randomly placed. The grid repeatedly prints to console, and the x/y coordinates of the vehicle objects updates on their threads which gives the impression of the vehicles animating across the grid-lanes.

    However, I'm stuck on how to make the vehicle objects respawn once they've reached the end of the grid. Any ideas how I can achieve this? Here's a screen shot and the code:

    grid.png

    public class gridMain {
     
        public static void main(String[] args) {
     
     
            Grid grid = new Grid(10, 20);
     
            Vehicle1 v1 = new Vehicle1(grid);
            Vehicle2 v2 = new Vehicle2(grid);
            grid.setVehicles(v1, v2);
     
     
            while(true) {
     
                grid.printGrid();
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
     
     
        }
    }
     
     
    public class Grid {
     
         //Grid width and height
        private int rows;
        private int columns;
        private String[][] gridArray;
        Vehicle1 v1;
        Vehicle2 v2;
     
     
    public Grid(int rows, int columns) {
        this.rows = rows;
        this.columns = columns;
        gridArray = new String[rows][columns];
    }
     
    public int getRows() {
        return rows;
    }
     
    public int getColumns() {
        return columns;
    }
     
    public void setVehicles(Vehicle1 v1, Vehicle2 v2) {
        this.v1 = v1;
        this.v2 = v2;
        startVehicles();
    }
     
    public void startVehicles() {
        Thread t = new Thread(v1);
        t.start();
     
        Thread t2 = new Thread(v2);
        t2.start();
    }
     
     
     
    public void printGrid() {
     
     
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                if (i == v1.getX() && j == v1.getY()) {
                    gridArray[v1.getX()][v1.getY()] = "o|";
     
                } else if (i == v2.getX() && j == v2.getY()) {
                    gridArray[v2.getX()][v2.getY()] = "x|";
     
                } else {
                        gridArray[i][j] = " |";
                    }
                }
            }
     
        System.out.println();
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                System.out.print(gridArray[i][j]);
            }
            System.out.println();
       }
    }
     
     
    }
     
    public class Vehicle1 implements Runnable {
     
    private int x; //Horizontal coordinate of vehicle
    private int y; //Vertical coordinate of vehicle
    private Grid g;
    private int speed;
     
     
    public Vehicle1 (Grid g) {
        int max = g.getRows();
        this.x = (int)(Math.random() * (max));
        this.y = 0;
        this.g = g;
        this.speed = (int) (200 + (600 - 200 ) * Math.random());
    }
     
    public int getX() {
    return x;
    }
     
    public int getY() {
        return y;
    }
     
    @Override
    public void run() {
     
     
        for(int i = y; i < g.getColumns(); i++) {
            y++;
            try {
                Thread.sleep(speed);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
     
    }
    }

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Respawn moving objects on 2D array

    Where is the definition for the class: Vehicle2?

    Why are there 2 Vehicle classes? Why not have 2 instances of the same class?

    respawn once they've reached the end of the grid
    What does respawn mean?
    Change direction of movement?
    Start moving from a new location?
    Or what???
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Respawn moving objects on 2D array

    Hi, thanks for the reply. It's very similar to Vehicle1 - I was going to try and understand the respawning problem then probably tidy everything with a Vehicle superclass. I'm kind of at the rough-sketching stage of this puzzle, eventually I'd like lots of lockable vehicle threads letting each other cross the intersecting lanes. By respawn, I mean a new instantiation of a Vehicle object - in the Vehicle class is a random generator which chooses a random lane for the Vehicle objects to start in. I'm trying to figure out a loop which would continuously create new Vehicle objects:

    public class Vehicle2 implements Runnable {
     
        private int x; //Horizontal coordinate of vehicle
        private int y; //Vertical coordinate of vehicle
        private Grid g;
        private int speed;
     
        public Vehicle2 (Grid g) {
            int max = g.getRows();
            this.x = 0;
            this.y = (int)(Math.random() * (max));
            this.g = g;
            this.speed = (int) (200 + (600 - 200 ) * Math.random());
        }
     
        public int getX() {
            return x;
        }
     
        public int getY() {
            return y;
        }
     
        @Override
        public void run() {
            for(int i = x; i < g.getColumns(); i++) {
                x++;
                try {
                    Thread.sleep(speed);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    Last edited by Lylio; February 13th, 2018 at 03:01 PM. Reason: Clarifying my issue

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Respawn moving objects on 2D array

    Is there a max number of vehicles that can be running?

    The current program is hard coded to have 2 vehicles. Change it to use a list that holds the current live vehicles.
    If you want to spawn a new vehicle when a vehicle reaches the edge, create the new vehicle and add it to the list and remove the vehicle that got to the edge.

    Also posted at: https://coderanch.com/t/690676/java/...-array#3242094
    and here: http://www.dreamincode.net/forums/to...s-on-2d-array/
    If you don't understand my answer, don't ignore it, ask a question.

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