ArrayList.toArray(); object vs int

Programming Questions

leerraum

ArrayList.toArray(); object vs int

in Programming Questions • 3 years ago

Hi,

I'm new to Processing, so I hope this goes to the right board.

I'm adding pixels from an image array to an arrayList called pixel. My purpose is to sort all the pixels in a special way. After I've ensured where to place them in the img.pixels array I'm storring them in a arrayList called pixel (just because Processing doesn't seem to perform basic array operations like pop, push, slice, etc.).

pixel.add(where, img.pixels[x]);

First Question: Is it a problem if I leave some positions in the arrayList void? i.e.: [0] = 1, [1]= nothing in here, [2]=3 ... and so on... because the values don't come in a correct order from 0 to n. Processing isn't complaining about it, but I'm not sure.

I'm trying to apply the arrayList pixel to the pixels array of my image. But neither the arraylist.toarray method nor img.pixels[x] = pixel.get(x); works. It tells me that I cant assign an object to an integer, which sounds logical to me.

Second Question: How do I convert a Object delivered by the get() Method into an integer?

Thanks!
leerraum

Replies(5)

bjordal

Re: ArrayList.toArray(); object vs int

3 years ago

(just because Processing doesn't seem to perform basic array operations like pop, push, slice, etc.)

I'm sorry what? pop, push and slice are not basic array operations!

Anyways as far as your first question goes, im not sure actually... having null objects in a arraylist doesn't make much sense if you ask me (but who am i to say, right?). So if it is important to store the position of every int i guess you could create a holder object like:
class someHolder{
int theInt;
int pos;
//.. constructor and getter and setters..//
}
and then push those into the arraylist and then when you get/pop them you can get it's position that way. Or you could maybe use a HashList...

as far as the second question goes, when you add a int to an arraylist ( someList.add(1);) it is converter to a Integer so what you need to do is recast the returned object to a Integer so: int someInt = (Integer)someList.get(0);

leerraum

Re: ArrayList.toArray(); object vs int

3 years ago

thanks!

I tried Processing this Sunday the first time and I was shocked that it doesn't have pop, push etc in it's syntax. But the arrayList seems to be a proper alternativ.

Is there more to know about the (Integer) thing? Is this the usual way to cast variables as a certain type?

bjordal

Re: Re: ArrayList.toArray(); object vs int

3 years ago

I'm sorry about not being any constructive with this post but i just have to ask.

I was shocked that it doesn't have pop, push etc in it's syntax.

What language were you using before? Because (as i said) arrays do not have function like pop and push in any language so the fact that you were shocked shocks me. And on that note, if any language does have functions like pop/push on their arrays, then it's arrays aren't actually arrays but in fact something like an ArrayList but that they are calling it an array.

PhiLho

Re: ArrayList.toArray(); object vs int

3 years ago

If you get data out of order, but know the total size in advance, put it in a classical array.
You can then convert the array to an ArrayList later if you need advanced manipulation on the data set:
List list = Arrays.asList(dataArray);
There is also the reverse operation:
Integer[] da = list.toArray(new Integer[0]);
The new Integer is to provide the type of data to cast to.
int vs. Integer: the former is a primitive type, small and fast to use. The latter is an object, necessary because you can put only objects, not primitives in ArrayLists. In recent versions, Java (thus Processing) automatically convert between the two (boxing and unboxing).

leerraum

Re: ArrayList.toArray(); object vs int

3 years ago

this integer thing is not completly new to me, but I'm still puzzled by the way to cast an Integer. thanks :)

@bjordal: AS3, PHP, JavaScript. Nothing sophisticated but in case of AS3 very close if not "better" compared to Processing. Especially regarding the OOP features.

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