Thread: ArrayList problem, probably very simple.

Hi.
I hope you can help me with debugging this piece of code, cause I'm going crazy. I've only implemented the code needed. 'public Model' is the constructor. I have highlighted where the problem is.

private ArrayList<ArrayList<Integer>> healthypercell = new ArrayList<ArrayList<Integer>>();
private ArrayList<ArrayList<Integer>> curedpercell = new ArrayList<ArrayList<Integer>>();
 
public Model (){
		for (int i = 0; i < rowcol; i++) {
			ArrayList<Character> chr = new ArrayList<Character>();
			ArrayList<Integer> nr = new ArrayList<Integer>();
			//ArrayList<ArrayList<Agent>> tempag = new ArrayList<ArrayList<Agent>>();
			for (int j = 0; j < rowcol; j++) {
				chr.add(input);
				nr.add(0);
			}
			infectedpercell.add(nr);
			curedpercell.add(nr);
			healthypercell.add(nr);
			lattices.add(chr);
		}
 
		//System.out.println("hej");
		for (int i = 0; i < 5; i++) {
			System.out.println("hej");
			if (infected > 0) {
				sirsend = 'i';				
			}
			else {
				sirsend = 's';
			}
			agx = (int)(Math.random()*100);
			agy = (int)(Math.random()*100);
			agents.add(new Agent(agx,agy,sirsend));
			if (infected <= 0) {
				temp = healthypercell.get(agx).get(agy);
				temp2 = temp+1;
				healthypercell.get(agx).set(agy, temp2);
			}
			else if (infected > 0) {
				//System.out.println(infectedpercell);
				counter += 1;
				temp = infectedpercell.get(agx).get(agy);
				temp2 = temp+1;
				//System.out.println(temp2);
				infectedpercell.get(agx).set(agy, temp2);
				//if (counter == 5)
 
 
				}
			if (infected >= 0)
			infected -= 1;	
			}

//System.out.println(infectedpercell); Somehow both infectedpercell and healthypercell ends up with the exact same Arraylists.
//System.out.println(healthypercell);
}

Originally Posted by Norm

Please explain what the problem is. Show the program's output and explain what is wrong with it and what you want it to be.

Why do you expect them to be different?

Please edit your post and wrap your code with code tags:
[code=java]
YOUR CODE HERE
[/code]
to get highlighting and preserve formatting.

Hi, and thanks for the fast reply. I don't understand why they would end up the same, unless I've missed something. The reason is that I only add 5 variables to the ArrayList called infectedpercell, and I don't even add anything to healthypercell, since I only run the loop 5 times. I've been trying to debug this code for hours now.

Originally Posted by Norm

Can you post the program's output that shows what you are talking about?

			healthypercell.add(nr); //<<<<<<< adds something here

Did you try using Find to see it add() was called?

That is where I initiliaze the ArrayList<ArrayList<Integer>> with zeros. I don't really understand what you mean by using Find, but I'll google it.

Originally Posted by Norm

"Find" is often a menu item in and editor that is used to find a String in the text of the file being edited.
I used it to find the source line I posted.

You still need to do this:
Can you post the program's output that shows what you are talking about?

Oh, that find. Yeah but it was only called to initiate to zeros. The output is an ArrayList<ArrayList<Integer>> that shows the number of occurances in each cell. Since there are 10.000 cells, I will just give an example.

[[0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]] (First ArrayList healthypercell)
[[0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]] (Second ArrayList infectedpercell)

Originally Posted by Norm

Where are the contents of the two arraylists printed out?
For debugging: Ideally their contents should be printed before and changes made and after and changes are made so the results of the code between the two print statements can be seen.


Is that what was printed by the program or something you made up using copy and paste of bits here and there? It needs to be exactly what the program printed, not copied and pasted bits and pieces.

Print the contents of the arraylists at the start of the Model constructor and print them again at the end to show what changes the constructor made to their contents.

Hi. Thanks for your time, but my mate found the error. I used the same ArrayList in all ArrayList<ArrayList>

infectedpercell.add(nr);
curedpercell.add(nr);
healthypercell.add(nr);