# Java ArrayList methods

Remember that to add something at a certain index, use
```
listName.add(i, "Thing to be added");
``` 
where ```i``` is the index where you want the item added.<br><br>

To change an item at a certain index, use
```
listName.set(i, "New thing");
```
but remember that you can only change something at an existing index with this command. If the index doesn't exist yet, you'll get an Out of Bounds error.<br><br>

You can use the ```remove()``` method in two ways:
```
listName.remove(i);
// or
listName.remove("Thing to be removed");
```
Either with the index whose item you want removed or with the item itself.<br><br>

```.size()``` gives you the length of the ArrayList.<br>
```
listName.size();
```
This returns the number of items in the list.<br><br>

To return an item when you have its index, use ```.get()```
```
listName.get(i);
```
On the other hand, if you know the item but not the index, you can use ```.indexOf()```
```
listName.indexOf("Item I'm looking for");
```
<br><br>
And the constructor is as follows:
```
ArrayList<Non-PrimitiveType> listName = new ArrayList<Non-PrimitiveType>();
```