();
for (SupClass s : superArray) {
try {
array.add(s);
} catch (Exception e) {
}
}
```
The problem is that Processing knows that the objects that the for loop is iterating through are not necessarily SubClass objects so displays the message [The function “add()” expects parameters like: “add(SubClass)”] and does not allow the code to even begin running. Is this a problem with Processing, or is there some way that I need to rewrite my code so that Processing allows it to run?
I understand that instances of a subclass can be added to an ArrayList of their super class, but in this scenario I need the ArrayList to be made of SubClass.
---
### Author:  [@noahbuddy](https://discourse.processing.org/u/noahbuddy)
#### Post date: [June 14, 2018, 6:41pm UTC](https://discourse.processing.org/t/error-trying-to-add-super-class-objects-to-subclass-arraylist/964/2 "2018-06-14T18:41:02Z")
This is really a limit in how classes operate.
Processing (Java) knows how to look at a subclass as a super but not the other way around.
```
"All cars are vehicles but not all vehicles are cars."
```
If you needed to access a subclass-only function from your list of superclasses you can use something like this:
```
if (s instanceof SubClass)
{
((SubClass)s).subfunc();
}
```
See this note on [subclasses](https://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html)
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [June 14, 2018, 7:29pm UTC](https://discourse.processing.org/t/error-trying-to-add-super-class-objects-to-subclass-arraylist/964/3 "2018-06-14T19:29:33Z")
> [@RafeArnold](#):
>
> `ArrayList array = new ArrayList();`
For 99% of cases, it’s wrong to have Java containers w/o specifying its generic ``: ☢
> **[ArrayList / Reference](https://processing.org/reference/ArrayList.html)**
>
> An ArrayList stores a variable number of objects. This is similar to making an array of objects, but with an ArrayList, items can be easily added and removed from the ArrayList and it is…
```auto
import java.util.List;
static final int SUPS = 5;
final List supsOrSubs = new ArrayList(SUPS);
void setup() {
noLoop();
for ( int i = 0; i++ < SUPS; supsOrSubs.add(
random(1) < .5? new SupClass() : new SubClass()) );
}
void draw() {
for (final SupClass sc : supsOrSubs) println(sc);
}
class SupClass {
@Override String toString() {
return getClass().getSimpleName();
}
}
class SubClass extends SupClass {
}
```
---
### Author:  [@RafeArnold](https://discourse.processing.org/u/RafeArnold)
#### Post date: [June 14, 2018, 7:35pm UTC](https://discourse.processing.org/t/error-trying-to-add-super-class-objects-to-subclass-arraylist/964/4 "2018-06-14T19:35:48Z")
You’re absolutely right. I actually did type that but forget to block text the code so the formatting emitted that part of the code.
Thank you for pointing my mistake out.
---
### Author:  [@RafeArnold](https://discourse.processing.org/u/RafeArnold)
#### Post date: [June 14, 2018, 7:43pm UTC](https://discourse.processing.org/t/error-trying-to-add-super-class-objects-to-subclass-arraylist/964/5 "2018-06-14T19:43:05Z")
I suspected this might be the case. I was unaware of Java’s ‘explicit casting’ functionality but have now educated myself on the concept after reading through the note you provided.
Thank you very much for responding to my query; it is much appreciated.