return copy instead of referance to collection

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sakcee@gmail.com - 30 Apr 2007 22:47 GMT

is there a way to return a copy of collection instead of referance to
collection itself

I have a wrapper class to a collection('Big' HashMap) data structure.
I want to give an accessor method
but I want to return a copy of the structure instead of refernace to
structure

should I copy key by key?, can i use clone? is there a way to give
final referance so that user can not
chnage it?

which is better ?

thanks

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Daniel Pitts - 30 Apr 2007 22:52 GMT

On Apr 30, 2:47 pm, "sak...@gmail.com" <sak...@gmail.com> wrote:

> is there a way to return a copy of collection instead of referance to
> collection itself
[quoted text clipped - 11 lines]
>
> thanks

There are a few options.
Collections.unmodifiable* will give you a wrapper Map or Collection
which the client cannot modify. It will be a view of the existing
collection, so that if your code changes the Map, the unmodifiable map
will change, but any calls to set/put in the unmodifiable map will
through unsupported exception.

Alternatively, you can usually
public Map<T> getMap() {
return new HashMap<T>(oldMap);
}

Hope this helps.

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