Java: List insert of more than one object with same HASH

I'm having a bit of trouble with this one:

I need to override the hashCode() and equals(), resulting in some objects being "equal". That's the intended behavior, but i have collateral problems with collections (has expected...):

I work with an ArrayList, and inserting a duplicate object at a predefined index is not honored by the insert method. Instead it is inserted at the PREVIOUS position of the FIRST duplicated existing element.

Let's say i have
A
B
C

And i insert duplicate of A at index >0...

it will be inserted at index 0.
->A
A
B
C

Is this normal behavior?

Thanks.

EDIT: Object is inserted at right position. The TableViewer i'm using (org.eclipse.jface.viewers.TableViewer) was confusing me, because it defaults the edit t开发者_运维知识库o the FIRST duplicated element (and that makes some sense...).

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I think in the list it does not matter whether it's duplicate or not.

I think it depends whether we are doing (as to where they will end up in the list) -

list.add(obj);
//or
list.add(index, obj);
//or
list.set(index, obj);

Other than that for a List, it's the order in which we add the object to the list.

Because if we have list like

List list = ArrayList();

Than it doesn't matter what type of object we add into it, so it does not make any difference whether we have the hashCode and equals defined or not.

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no that isn't normal.

as far as i know, no implementation of java.util.List uses the equals() or hasCode() method

can you provide some code sniped please?

Maby you were looking at the first A you have prevously inserted?

A // prevously inserted 
B 
C 
A // the new duplicat