JDK 8 code review request for 7140820 Add covariant overrides to Collections clone methods

[Joe Darcy]

On 01/30/2012 04:19 AM, Tom Hawtin wrote:
> On 30/01/2012 03:58, Joe Darcy wrote:
>
>> Object clone()
>>
>> method inherited from java.lang.Object with a covariant override such as
>>
>> MyType clone()
>
> This is, of course, going to break any existing overrides (that aren't 
> making use of covariant return types). This will be why the changes 
> weren't made way back in 1.5.

While this issue may have good technical grounding, there were also many 
potential changes omitted from JDK 5 due to lack of time, etc.

>
> Other clone implementations are overridden for (mobile code) security 
> reasons. These methods may have the same thing done to them by trusted 
> code outside of the Java library.
>
> A better solution to the unchecked casts from clone, is not to clone. 
> Using a constructor gets rid of the problem, and ensures you aren't 
> using some funky (potentially malicious) subclass.
>
> -            return (Hashtable<String, java.lang.Object>)_env.clone();
> +            return new Hashtable<>(_env);
>
> Tom

I suppose this depends on what your threat model is.  For better or 
worse, the types in question are Cloneable and should have reasonable 
clone methods.

-Joe