[jira] [Commented] (GROOVY-9003) Allow the override of toString and equals methods for collection objects

["Paul King (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-9003?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16773463#comment-16773463 ] 

Paul King commented on GROOVY-9003:
-----------------------------------

Overlaps with GROOVY-4653 and GROOVY-8756.

> Allow the override of toString and equals methods for collection objects 
> -------------------------------------------------------------------------
>
>                 Key: GROOVY-9003
>                 URL: https://issues.apache.org/jira/browse/GROOVY-9003
>             Project: Groovy
>          Issue Type: Improvement
>            Reporter: paolo di tommaso
>            Priority: Major
>             Fix For: 3.x
>
>
> Groovy provides a nice string representation for collection objects, however the current behaviour do not allow custom collection classes to provide own string representation not to implement a custom object identity rule.
> For example:
> {code:java}
> class Mylist extends ArrayList {
>   Mylist(Collection c) { super(c) } 
>   @Override boolean equals(Object o) { throw new UnsupportedOperationException () }
>   @Override int hashCode() { throw new UnsupportedOperationException () }
>   @Override String toString() { return 'CUSTOM STRING' }
> }
> def l = new Mylist([1,2,3]) 
> assert l.toString() == 'CUSTOM STRING'
> assert "$l" == '[1, 2, 3]'
> def q = new Mylist([1,2,3])
> assert l.equals(q)
> assert l == q 
> {code}
> In the {{Mylist}} class the {{toString}} method is not invoked in the string interpolation and {{equals}} is not invoked by the {{==}} operator. This breaks the java polymorphism contract and create several hassles when implementing custom collection classes.
>  I would propose to fix this behaviour in Groovy 3.0. It would be enough to check in the target class implements the {{toString}} and {{equals}} methods otherwise fallback on the current Groovy behaviour.
>  



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