Do either of you know how to use Greenfoot?

Never used it before, but I just read over the intro at their site and it looks like a pretty basic learning tool for object-oriented programming. Got a specific question?

Yes, you remember that old asteroid game where you control a ship and with that ship you just blow up asteroids to keep yourself alive.

Well, as of now, I need to generate 2 rockets and 3 asteroids at random places. I don't know how to generate them at random locations and I'm trying to attempt to use what I learned from Wombats and Leaves, but it isn't working.

I haven't used it and I'm not sure what API is given, but if you go into the constructors for your Rocket and Asteroid classes there may be an overridden constructor that takes start location as a parameter (probably as a (x,y) pair). If so, call that with a randomization function with the parameters being the width and height of the grid. If not, you may have to write that new constructor yourself, depends on how much they give you to start.

public class Space extends World
{
public Space()
{
super(600, 400, 1);
GreenfootImage background = getBackground();
background.setColor(Color.BLACK);
background.fill();
createStars(300);
Explosion.initialiseImages();
}

private void createStars(int number)
{
GreenfootImage background = getBackground();
for(int i=0; i < number; i++) {
int x = Greenfoot.getRandomNumber( getWidth() );
int y = Greenfoot.getRandomNumber( getHeight() );
int color = 150 - Greenfoot.getRandomNumber(120);
background.setColorAt(x,y,new Color(color,color,color));
}
}
}

I was only given this for the world.
When I randomized the places that Wombats would spawn, I was told to do it within the world--Wombat World.

In this case, it would be the Space world since the background given to me is space and stars were created as I can see.
I attempted to use the same format and such for Asteroids and Rockets but failed.

I got it.

Never used Greenfoot, but it looks pretty cool/simple. The interface and concept remind me, in a way, of Labview.

It looks just like "stagecast" that thing was the shit when i didnt know how to code in an actual language.