JAVA: Randoming amount of objects added to World - Overclock.net

ninjinsamax3 · 10-16-09

I need help on randomizing the number of objects added to the world.

public void addedToWorld(World world)
{
this.world = (AlienWorld)world;
setImage(new GreenfootImage(1, 1));
aliens = new HashSet<Alien>();
for(int i = getX() ; i<=getX()+800 ; i+=50) {
for(int j = getY() ; j<getY()+(ROWS*(Greenfoot.getRandomNumber(50)+1)) ; j+=50) {
Alien alien = new Alien();
world.addObject(alien, i, j);
aliens.add(alien);
}
}
}

Some things to know is that ROWS = 3, so basically there will be 3 rows.
The first row according to this code, adds a whole row of aliens which means it is not randomizing at all.
The second and third row does do what it is doing, randomizing the amount in the row and also the position.

Example: O = object X = space/empty slot
OOOOOOOOOO
OOXOXXOOOXO
XOOOOXOXXXO

When I reset the scenario:
OOOOOOOOOO
XOXOXXOOXOO
OOOXOXXOOXO

When I reset the scenario only row 2 and 3 are randomizing, but the first row is not, and I have no idea how to fix it, anyone know?

Thanks

adramalech707 · 10-16-09

okay well i don't know if this will work but maybe what you need to do is think about the random number generator....see if the random number generator isn't setup correct or what not you will get repeats......

another tip is maybe name objects different than the objects name.....so it has better readability...

http://java.sun.com/j2se/1.4.2/docs/...il/Random.html

this is the java doc for random...which is the superclass for anything about random number generators and what not....

what you got to worry about is this part....which i quote directly from the documentation of random class

Quote:

If two instances of Random are created with the same seed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers. In order to guarantee this property, particular algorithms are specified for the class Random. Java implementations must use all the algorithms shown here for the class Random, for the sake of absolute portability of Java code. However, subclasses of class Random are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.

so pretty much gotta worry about the generator mutating and showing bad cases of repetition

dharmaBum · 10-16-09

Out of context it isn't too easy to parse your code. But I'll give it a shot.

If I'm understanding you're problem, it's that the first row is consistently being filled with objects. This is expected from how you're "for" loop is set up:

Code:

for(int j = getY() ; j<getY()+(ROWS*(Greenfoot.getRandomNumber(50)+1)) ; j+=50) {...}

Notice: getY()+(ROWS*(rand(50)+1)) > getY(), because the minimum of (ROWS*(rand(50)+1)) is ROWS. And getY < getY + ROWS.

So this loop will always execute one iteration, so you're always going to get a first row full of objects.

At this point I'm not sure if you're trying to completely randomize each spot on a column, or have a "random amount" in each (that is, each column gets either 0,1,2,3 objects filling up from the bottom). Using a for loop in the manner you have suggests the later, but your comment suggests the former (in which case just iterate through the rows and do a "coin flip" to decide if to add an object or not).

ninjinsamax3 · 10-16-09

Yeah I noticed that problem in the for loop afterward, but I have no idea how to fix this issue. Would you happen to know how I can make it randomized all over the place?

The quesiton that I was asked to do was ambiguous. It only said to make the objects have a random amount. Originally it has liek 3 rows and I believe 17 column, so that makes 51 objects. In the pattern shown above.

I would have put the other classes, but there was too much to put since most were prefilled and i was only assigned to edit some parts.

dharmaBum · 10-16-09

Quote:

Originally Posted by ninjinsamax3

Yeah I noticed that problem in the for loop afterward, but I have no idea how to fix this issue. Would you happen to know how I can make it randomized all over the place?

The quesiton that I was asked to do was ambiguous. It only said to make the objects have a random amount. Originally it has liek 3 rows and I believe 17 column, so that makes 51 objects. In the pattern shown above.

I would have put the other classes, but there was too much to put since most were prefilled and i was only assigned to edit some parts.

If it's supposed to just assign random throughout, then the solution is pretty easy (using simplified code).

Code:

//assume the object array has been initialized to all empty.
void randomize()
{
   int coinflip;
   for(int i=0;i<ROWS;i++)
   {
      for(int j=0;j<COLUMNS;j++)
      {
          //here my_random will return 0 or 1
          coinflip=my_random(1);
          //if 1, add object
          if(coinflip==1)
          {
              add_object(i,j);
          }
       }
}

Is this close to what you're looking to do?

ninjinsamax3 · 10-17-09

To me it seems great, I didn't think abotu this.

My professor just want's it to have a random amount of objects, instead of all the rows having objects. I guess thsi would work. I will try this on monday when I have access to Uni computers! Thanks a lot.

edit:
Your idea worked great! Thanks again!

		Overclock.net - Overclocking.net > Software, Programming and Coding > Coding and Programming > Application Programming
JAVA: Randoming amount of objects added to World

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)