Array of classes, subclasses of specific class

Question

I have got an array of Classes, declared as follows:

Class<?>[] serviceStack = {GetPlanningData.class, GetTimeTable.class, GetDataToSync.class, GetData.class};

Classes GetPlanningData, GetTimeTable, GetDataToSync and GetData are all subclasses of IntentService.

Can I declare an array of subclasses of IntentService? I tried:

Class<? extends IntentService>[] serviceStack;

and

Class<IntentService>[] serviceStack;

but the first one is a "Generic array creation", as Android Studio says, and the second one permits only to create {IntentService.class, IntentService.class, ...} and no subclasses are allowed.

EDIT: I am programming in Android, and the main goal of this is to call Services sequantially. So I put this array as an extra of the first Service and when the service has finished I call the first element of the array, passing the array without the first element.

This works, but I can't use Lists because I can't put a List extra to a Context.

I would work around the issue and create a generic collection instead. Something in the lines of List<? extends IntentService>. — Mena
– Mena, Commented Aug 31, 2015 at 10:26
I have to call a series of IntentService sequentially, but I can't use a List (that'd be great) because, programming on Android, I can't put a List "extra". — Simone Chelo
– Simone Chelo, Commented Sep 4, 2015 at 9:46

Tagir Valeev · Accepted Answer · 2015-08-31 10:38:24Z

2

Do not use array. Create a List instead:

List<Class<? extends IntentService>> serviceStack = Arrays.asList(
    GetPlanningData.class, GetTimeTable.class, 
    GetDataToSync.class, GetData.class);

This way you will be type-safe.

answered Aug 31, 2015 at 10:38

Tagir Valeev

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1 Comment

Simone Chelo Over a year ago

That would be great, but I can't use Collections, because programming on Android I have to put this array in an extra, and I can't put a list in a extra.

user1606576 · Accepted Answer · 2015-08-31 10:34:22Z

2

I think this answers your question:

You cannot create arrays of parameterized types

source:

https://docs.oracle.com/javase/tutorial/java/generics/restrictions.html#createArrays

answered Aug 31, 2015 at 10:34

user1606576

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1 Comment

Andy Brown Over a year ago

That is unfortunately not strictly true: to be precise you cannot directly instantiate arrays of non-reifiable types. You can therefore instantiate an array like new Foo<?>[1] as it is reifiable (the only reifiable parameterized type is an unbounded wildcard parameterized type).

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