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From "Homer Jay (JIRA)" <j...@apache.org>
Subject [jira] [Created] (LANG-1261) ArrayUtils.contains returns false
Date Tue, 23 Aug 2016 08:33:20 GMT
Homer Jay created LANG-1261:
-------------------------------

             Summary: ArrayUtils.contains returns false
                 Key: LANG-1261
                 URL: https://issues.apache.org/jira/browse/LANG-1261
             Project: Commons Lang
          Issue Type: Bug
          Components: lang.*
    Affects Versions: 3.4
         Environment: Android
            Reporter: Homer Jay


ArrayUtils.contains(Object[] array, Object objectToFind) wrongly returns false.

STEPS TO REPRODUCE
=========================================================
-Create a superclass "Parent" and override equals and hashcode based on some member id variable.
-Create a class "Child" extending "Parent". Do not override equals nor hashcode.

-Let "childrens" be an array of type Child[] containing several instances.
Create an instance of Parent "p" with the same id as childrens[0], such that childrens[0].equals(p)
returns true and p.equals(childrens[0]) returns true as well.

Because they are equals, ArrayUtils.contains(childrens, p) should return true. However it
returns false.


WHERE THE BUG IS LOCATED
=====================================================
-Go to ArrayUtils.class, line 1917. In the "indexOf" method implementation, before going into
calling equals for each element of the input array, there is some sort of optimization check
to make sure the instance to be found is an instance of the array type:

} else if (array.getClass().getComponentType().isInstance(objectToFind)) {

That line is wrong. In our case, the array contains elements of type "Child", whereas the
object to be found is of type "Parent". They are equals according to the equals implementation
of "Parent", but obviously Children.class.isInstance(p) is false.


EXPECTED BEHAVIOR
================================================
Since the method signature accepts an array of Object[] and an instance of Object, it should
ignore the classes of the arguments. It should be possible to call "ArrayUtils.contains(Child[]
children, Parent p)", in fact it should be possible to do this with any combination of classes,
not only the ones assignable from the class hierarchy.



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