Processing 1.0 - Processing Discourse - Variables of objects from ArrayList

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Variables of objects from ArrayList (Read 568 times)

Al_11

Variables of objects from ArrayList
Feb 7^th, 2009, 5:19am

Hello guys! Could someone help who has some exp about working with objects from ArrayList. Please tell where can read about:
1) How to define object's index in ArrayList?
(When using loop: for(int i; i<list.size()...)
2) How to work with objects' inner variables, when
objects placed in ArrayLists?
3) How to communicate 2 diff objects' variables from 2
diff ArrayLists?

I've found interesting topic for me:

http://forums.sun.com/thread.jspa?forumID=31&threadID=5193767

Citation:

" Are you trying to do 1 or 2?
1. Given a bunch of records, look up tom's in particular and do something with it.
or
2. Given a bunch of records, go through them all and do something with each record in turn."

Unfortunally 2nd question descripted there, when I need 1st.

And the last question: What is better for me from there:

for(TaxRecord record : records) {
int income = record.getIncome();
//...
}

for(Iterator <TaxRecord > i = records.iterator(); i.hasNext(); ) {
TaxRecord record = i.next();
int income = record.getIncome();
//...
}

for(int j = 0; j < records.size(); ++j) {
TaxRecord record = records.get(j);
int income = record.getIncome();
//...
}

PhiLho

Re: Variables of objects from ArrayList
Reply #1 - Feb 7^th, 2009, 11:40am

Warning! The new syntax (for (i : I), I<C>) isn't supported in Processing, unless you use it in .java files.

I am not sure to understand 1), but there is a add(int index, E element) method in ArrayList. Unlike a pure array, this add pushes up the previous elements and you cannot add at arbitrary places, only within the size().
Example:
Code:

ArrayList al = new ArrayList(10);

// If I don't put this line, the add below will throw an error
for (int i = 0; i < 10; i++) al.add(">--" + i);

al.add(1, "One");
al.add(3, "Three");
al.add(5, "Five");
al.add(8, "Eight");

ListIterator it = al.listIterator();
while (it.hasNext())
{
  int i = it.nextIndex();
  String s = (String) it.next();
  println(i + " " + s);
}

2) In old syntax, when you do a get() (or a next()), you have a generic Object. You have to cast (like above) the object to its real type to be able to access the inner variables (fields of the class).

3) I am not sure to understand the question.

Al_11

Re: Variables of objects from ArrayList
Reply #2 - Feb 7^th, 2009, 5:28pm

Thank you PhiLho.
About my main question: For example I have 2 different undefined ArrayLists, one of them holds circles and other boxes - this objects created form their classes. But each object brings it's undefined color and and it's height - this variables are inner for class created from. When circle stamps to the box - how to make circle get color and height of current box? How circle can get current index of box?
When I work I use everywhere "for(int i; i<AList.size();..."

Maybe everything have to work - maybe I'm just "parked in the rong place"?

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: Variables of objects from ArrayList Reply #3 - Feb 7^th, 2009, 6:35pm Within the loop, you get the nth object with: Box b = (Box) listOBoxes.get(n); and same for circles. Then you can access any data within the object(s), as usual.

Al_11 Junior Member Offline Posts: 75	Re: Variables of objects from ArrayList Reply #4 - Feb 7^th, 2009, 10:40pm I got it, thank you, I just was stumped...

Al_11

Re: Variables of objects from ArrayList
Reply #5 - Feb 8^th, 2009, 3:20am

I've solved that...
But may I ask you again? It's intresting topic for me...
I made 2 loops inside class Circle:

1st within mouseDragged { ( for int n;...) { Box b = (Box) listOBoxes.get(n);...

2nd within mouseReleased { ( for int n;...) { Box b = (Box) listOBoxes.get(n);...

Index of boxes is missed and I can't catch up how to make 1st and 2nd loop to collaborate when there are 2 loops. Should it work in further?

Will this be a good idea to create new void mouseAct() { dragged, pressed, etc.) for using 1 loop there?

PhiLho

Re: Variables of objects from ArrayList
Reply #6 - Feb 8^th, 2009, 4:55pm

Quote:

Index of boxes is missed and I can't catch up how to make 1st and 2nd loop to collaborate when there are 2 loops.

I fear I don't get it. What do you mean "index is missed"? And what kind of collaboration?

But in general, yes, if you do twice the same thing, it is a good idea to make a more general function and call it where needed.

Al_11 Junior Member Offline Posts: 75	Re: Variables of objects from ArrayList Reply #7 - Feb 11^th, 2009, 6:25am I got it. Thank you.

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