Java - name of ArrayList?

Question

I've the following question:

Why is it not necessary to use a name of the list before the add-statement (add (pipedInstanceIterator.next())) ?

Thanks.

public class InstanceList extends ArrayList<Instance> implements Serializable, Iterable<Instance>, AlphabetCarrying
...
public void addThruPipe (Iterator<Instance> ii)
{
    //for debug
    Iterator<Instance> pipedInstanceIterator = pipe.newIteratorFrom(ii);
    while (pipedInstanceIterator.hasNext())
    {   
        add (pipedInstanceIterator.next());
        //System.out.println("Add instance " + pipedInstanceIterator.next().getName());
    }
}

You're extending ArrayList, so the method is implicitly called on this. — Reinstate Monica -- notmaynard
– Reinstate Monica -- notmaynard, Commented Jun 11, 2015 at 14:26

Eran · Accepted Answer · 2015-06-11 14:25:56Z

1

Your InstanceList is a sub-class of ArrayList, so it can execute any public or protected methods of that class without specifying the instance for which they should be executed.

answered Jun 11, 2015 at 14:25

Eran

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4 Comments

CyKon Over a year ago

Okay. One last question: Is it because of the Collection ArrayList or does it apply in general (relationship supper - sub class)?

Eran Over a year ago

@user3680103 it applies to any sub-class.

CyKon Over a year ago

But why does it not work if I call the add-method at the main-method and it gives the warning "cannot cast a static to a non-static reference" ?

Eran Over a year ago

@user3680103 Because the main method is static, so it doesn't have a reference to any instance of InstanceList.

JShell · Accepted Answer · 2015-06-11 14:26:55Z

0

Because InstanceList extends ArrayList, any unspecified methods will be run on it. So your adding to instance list

answered Jun 11, 2015 at 14:26

JShell

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2 Comments

CyKon Over a year ago

But why does it not work if I call the add-method at the main-method and it gives the warning "cannot cast a static to a non-static reference" ?

JShell Over a year ago

In what context do you get this error? It usually happens when you try to call a method from class(add), not from object of that class (e.g. InstanceList)

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