Interfaces in Java

Question

So I have a class cat which implements a interface Vocal, I was wondering why when I created a ArrayList(Vocal) I was able to add instances of cat to it?

Thank You

Take a look at covariance as this is what is going on here.

Suroot
– Suroot

2011-06-15 04:13:17 +00:00
Commented Jun 15, 2011 at 4:13 — Suroot
– Suroot, Commented Jun 15, 2011 at 4:13

Cameron Skinner · Accepted Answer · 2011-06-15 04:04:46Z

It's because when Cat implements Vocal it's an IS-A relationship: Cat IS-A Vocal.

Since the List<Vocal> accepts anything that is Vocal, adding an instance of Cat is perfectly legal.

Asaph · Accepted Answer · 2011-06-15 04:10:03Z

1

Yes. You will be able to add an instance of any class that is declared to implement Vocal.

edited Jun 15, 2011 at 4:10

Asaph

163k25 gold badges204 silver badges204 bronze badges

answered Jun 15, 2011 at 4:04

Ted Hopp

235k48 gold badges412 silver badges533 bronze badges

Comments

gmhk · Accepted Answer · 2011-06-15 04:14:23Z

In your case, the relationship will be exactly the same

Cats IS A Vocal too.

So that was the reason you are able to add the arraylist of CATS in Vocal Type Arraylist

Collectives™ on Stack Overflow

Interfaces in Java

3 Answers 3

Comments

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Related