# How to access the sub-arrays of an Array list?
**URL:** https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695
**Category:** Beginners
**Created:** [February 10, 2020, 5:36pm UTC](https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695 "2020-02-10T17:36:36Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@solub](https://discourse.processing.org/u/solub)
#### Post date: [February 10, 2020, 5:36pm UTC](https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695/1 "2020-02-10T17:36:37Z")
Hi,
Can someone kindly explain how to access the sub arrays of an ArrayList in Processing Java ?
The example below throws a casting error when I try to get of the sub-arrays at a specific index.
> cannot convert from Object to ArrayList
```auto
PVector p1 = new PVector(100, 620);
PVector p2 = new PVector(700, 720);
PVector p3 = new PVector(120, 520);
PVector p4 = new PVector(500, 290);
void setup() {
size(800, 800);
ArrayList tlist = new ArrayList();
tlist.add(new PVector[]{p1,p2});
tlist.add(new PVector[]{p2,p3});
tlist.add(new PVector[]{p3,p4});
for (int i = 0; i < tlist.size(); i++) {
ArrayList edge = tlist.get(i); //<-- throws an error
}
}
```
---
### Author:  [@cansik](https://discourse.processing.org/u/cansik)
#### Post date: [February 10, 2020, 5:46pm UTC](https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695/2 "2020-02-10T17:46:47Z")
Ok, there are some things missing. First of all, I would suggest to always specify the type of your `ArrayList`, because it makes working with it way easier and the compiler understands it too.
`ArrayList` is a generic class which manages list of things. It does not matter if it is an apple or a cat, a list of cats and a list of apples are managed the same way (adding items, removing items, listing items). If you do not specify a type, the `ArrayList` just uses the most-generic type possible. Because every object in java is a child of `Object`, it will use this type.
Because you want to store Arrays of Vectors inside your Arraylist, I would suggest you define the type of your list as `PVector[]`:
```java
ArrayList tlist = new ArrayList();
```
The second problem is, that you try to get an element of the list, but try to store it into the wrong variable type. The following code would only work, if your list contains items which are arraylists too (like `ArrayList`).
```java
ArrayList edge = tlist.get(i);
```
But your list contains arrays of vectors (`PVector[]`), so it won’t work to cast a `PVector[]` into a variable of type `ArrayList`. Change the variable type to `PVector[]` and your are good to go:
```java
PVector[] edge = tlist.get(i);
```
---
### Author:  [@solub](https://discourse.processing.org/u/solub)
#### Post date: [February 10, 2020, 5:52pm UTC](https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695/3 "2020-02-10T17:52:33Z")
Thank you for the swift reply and the comprehensive explanation, it helps a lot.
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [February 10, 2020, 7:03pm UTC](https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695/4 "2020-02-10T19:03:24Z")
Here’s my take on it: 😳
```auto
import java.util.List;
final List pairs = new ArrayList();
final PVector[] points = {
new PVector(50, 310),
new PVector(350, 360),
new PVector(60, 260),
new PVector(250, 145)
};
void setup() {
size(400, 400);
PVector p = points[0];
final int end = points.length;
int i = 0;
while (++i < end) pairs.add(new PVector[] { p, p = points[i] });
for (final PVector[] pair : pairs) println(pair);
exit();
}
```
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [February 10, 2020, 7:16pm UTC](https://discourse.processing.org/t/how-to-access-the-sub-arrays-of-an-array-list/17695/5 "2020-02-10T19:16:45Z")
Now converted to Python Mode: 🐍
```auto
pairs = []
points = (
PVector(50, 310),
PVector(350, 360),
PVector(60, 260),
PVector(250, 145))
def setup():
size(400, 400)
p = points[0]
for i in range(1, len(points)):
v = points[i]
pairs.append((p, v))
p = v
for pair in pairs: print pair
exit()
```