ArrayList Processing - How to access each index separately - arraylist

Question

As it is a first time I'm using ArrayList in Processing I'm experiencing some issues.
I have created an Arraylist that stores a PVector (x,y position) of an Ellipsee.
What I'm trying to do is very simple I think but I can't find much info on ArrayLists.
Code:
ArrayList position;
void setup()
{
position= new ArrayList<Vectors>();
}
void draw()
{
position.get(i).display(); //display ellipse
}
void mousePressed()
{
position.add(new Vectors(new PVector(mouseX, mouseY)));
}
So every time mouse is Pressed a new ellipse is created at mouseX mouseY position. What I would like to do is when my I created an amount ellipses, I need to control each one separately to change it's size or color either by clicking on them or with KeyPressed().

Answer 1

This won't compile automatically as I'm assuming your PVector object has already been created and that it has two public attributes of xPosition and yPosition:
// Initialise your arraylist
ArrayList<PVector> listOfPVectors = new ArrayList<PVector>;
// Objects can be added to your list as follows:
PVector pvectorObject = new PVector();
listOfPVectors.add(pvectorObject);
// The size of your ArrayList can be output as follows:
println(listOfPVectors.size());
// You can iterate through every entry in the arraylist as follows:
for(int index = 0; index < listOfPVectors.size(); index ++) {
println("X Position Value = " + listOfPVectors.get(index).xPosition);
println("Y Position Value = " + listOfPVectors.get(index).yPosition);
}
Basically, you use the ArrayList.get(indexPosition) method to retrieve any element you want from your ArrayList. You can then work away with it as normal.
Hope this helps!