Random number issue

Question

I'm making a mobile game and I can't seem to generate a random number successfully
Game.java:
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
public class Game extends MIDlet implements CommandListener {
private Display theDisplay;
private GameCanvas canvas;
private Player p1;
private Block[] Grid;
static final Command exitCommand = new Command("Exit", Command.STOP, 1);
class Player {
  public int x, y;
  public int width=60, height=15;
  public Player(int curX, int curY) {
   x = curX;
   y = curY;
public Game() {
  setupGrid(5, 8, 5);
  p1 = new Player(90, 250);
  theDisplay = Display.getDisplay(this);
private void setupGrid(int rows, int cols, int cellspacing) {
  Grid = new Block[200];
  int ind = 0;
  int posX = 10;
  int posY = 20;
  int colPosY;
  int colPosX;
  colPosY = posY;
  colPosX = posX;
  for(int x = 0; x < rows; x++) {
   Grid[ind] = new Block(posX, posY);
   colPosY = posY;
   for(int y = 0; y < cols; y++) {
    ind++;
    colPosX += 20+cellspacing;
    colPosY = posY;
    Grid[ind] = new Block(colPosX, colPosY);
   colPosX = posX;
   posY += 15+cellspacing;
   ind++;
class Block {
   public int x, y;
   public int Health;
   public int r = 0, g = 0, b = 0;
   public Block(int curX, int curY) {
   x = curX;
   y = curY;
   double rand = Math.random()*5;
   if(rand > 0 && rand < 2) {
    g = 255;
    r = 0;
    b = 0;
   if(rand > 2 && rand < 4) {
    r = 255;
    g = 0;
    b = 0;
   if(rand > 3 && rand < 5) {
    b = 255;
    g = 0;
    r = 0;
class GameCanvas extends Canvas {
  private int width;
  private int height;
  GameCanvas() {
   width = getWidth();
   height = getHeight();
  public void paint(Graphics g) {
   g.setColor(0, 0, 0);
   g.fillRect(0, 0, width, height);
   g.setColor(100, 100, 100);
   g.fillRect(p1.x, p1.y, p1.width, p1.height);
   for(int x = 0; x < Grid.length; x++) {
    if(Grid[x] != null) {
     g.setColor(Grid[x].r, Grid[x].g, Grid[x].b);
     g.fillRect(Grid[x].x, Grid[x].y, 20, 10);
  public void keyPressed(int keyCode) {
   int key = getGameAction(keyCode);
   if(key == LEFT && p1.x > 0) {
    p1.x-=4;
   else if(key == RIGHT && p1.x < canvas.width-p1.width) {
    p1.x+=4;
   repaint();
protected void startApp() throws MIDletStateChangeException {
  canvas = new GameCanvas();
  canvas.addCommand(exitCommand);
  canvas.setCommandListener(this);
  theDisplay.setCurrent(canvas);
public void pauseApp() { }
public void destroyApp(boolean unconditional) { }
public void commandAction(Command c, Displayable d) {
  if(c == exitCommand) {
   destroyApp(false);
   notifyDestroyed();
}Game.java:58: cannot find symbol
symbol : method random()
location: class java.lang.Math
double rand = Math.random()*5;
^
1 error
Line 58:
double rand = Math.random()*5;

Answer 1

b1nary wrote:
Unfortunately, no - it won't work. Prior to posting this thread I researched different ways to generate random numbers but, apparently, the WTK only allows certain packages to be recognized.You can always write your own generator. For portability I use
* Uniform random number generator.
* <p>
* Based on
* <blockquote>
* <pre>
* Efficient and Portable Combined Random Number Generators
* <a href="http://www.iro.umontreal.ca/~lecuyer">Pierre L'Ecuyer</a>
* Communications of the ACM
* June 1988 Volume 31 Number 6
* </pre>
* </blockquote>
* @author Sabre
public class Ecuyer
     * Constructs the generator based on two starting seeds.
     * <p>
     * Two generators using the same pair of seeds will produce
     * exactly the same sequence of pseudo random numbers.
     * @param seed1 the starting seed.
     * @param seed2 the second starting seed.
    public Ecuyer(int seed1, int seed2)
        s1 = (seed1 > 0) ? seed1 : 1;
        s2 = (seed2 > 0) ? seed2 : 1;
     * Constructs the generator based on a starting seed.
     * <p>
     * Two generators using the same seeds will produce
     * exactly the same sequence of pseudo random numbers.
     * @param seed the starting seed.
    public Ecuyer(long seed)
        this((int) ((seed >> 32) & 0x7fffffff), (int) (seed & 0x7fffffff));
     * Constructs a generator using the current time as seed.
    public Ecuyer()
        this(System.currentTimeMillis());
     * Returns the next random number
     * @return the next random number
    public double nextValue()
            // m = 2147483563, a = 40014
            int k = s1 / q1;
            s1 = a1 * (s1 - k * q1) - k * r1;
            if (s1 < 0)
                s1 += m1;
            // m = 2147483399, a = 40692
            int k = s2 / q2;
            s2 = a2 * (s2 - k * q2) - k * r2;
            if (s2 < 0)
                s2 += m2;
        int z = s1 - s2;
        if (z < 0)
            z += m1;
        return z * 4.656613e-10;
    static final int m1 = 2147483563;
    static final int a1 = 40014;
    static final int q1 = 53668;
    static final int r1 = 12211;
    static final int m2 = 2147483399;
    static final int a2 = 40692;
    static final int q2 = 52774;
    static final int r2 = 3791;
    private int s1;
    private int s2;
}Make sure you test it thoroughly before committing to it.