Get class from ArrayList

Question

I'm wondering how to change a variable inside an object in an ArrayList.

I have tried myList.get(i); but this returns an <Object> and I don't understand what to do this.

(Basically) What I have:

ArrayList list = new ArrayList();
Issue issue = new Issue();
list.add(issue);

What i want to access later, via the list:

issue.myString;

So to clarify, I have an instance of class Issue inside ArrayList list, and I want to change issue.myString

cast that object to Issue for example -> ((Issue)list.get(index)).myString — random_user
– random_user, Commented Nov 19, 2016 at 19:25
Lol... I thought I tried that but apparently I had just messed up the parentheses... — Oscar Lundberg
– Oscar Lundberg, Commented Nov 19, 2016 at 19:28

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

You have (at least) two options.

The list contains only issues

In that case, you can use a typed list:

List<Issue> list = new ArrayList<>();
Issue issue = new Issue();
list.add(issue);

This way, calls like list.get(i) will return an Issue.

List list = new ArrayList();
Issue issue = new Issue();
list.add(issue);
Object object = new Object();
list.add(object);

In that case, you'll have to check if the object is an Issue first.

Object rawItem = list.get(i);
if(rawItem instanceof Issue) {
    Issue issue = (Issue) rawItem;
    ...
}

CommunityBot

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answered Nov 19, 2016 at 19:38

duckstep

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larsgrefer · Accepted Answer · 2016-11-19 19:37:57Z

1

Use a typed list:

ArrayList<Issue> list = new ArrayList<>();
Issue issue = new Issue();
list.add(issue);

now list.get(i) will return <Issue> and not just <Object>

answered Nov 19, 2016 at 19:37

larsgrefer

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