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From "paolo di tommaso (JIRA)" <>
Subject [jira] [Created] (GROOVY-9003) Allow the override of `toString` and `equals` methods for collection objects
Date Wed, 20 Feb 2019 07:57:00 GMT
paolo di tommaso created GROOVY-9003:

             Summary: Allow the override of `toString` and `equals` methods for collection
                 Key: GROOVY-9003
             Project: Groovy
          Issue Type: Improvement
            Reporter: paolo di tommaso
             Fix For: 3.x

Groovy provides a nice string representation for collection objects, however this implementation
do not allow to custom collection class to override their own string representation.

For example:

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 


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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