== Why is this an issue?

Comparisons of dissimilar types will always return false. The comparison and all its dependent code can simply be removed. This includes:

* comparing an object with null
* comparing an object with an unrelated primitive (E.G. a string with an int)
* comparing unrelated classes
* comparing an unrelated ``++class++`` and ``++interface++``
* comparing unrelated ``++interface++`` types
* comparing an array to a non-array
* comparing two arrays

Specifically in the case of arrays, since arrays don't override ``++Object.equals()++``, calling ``++equals++`` on two arrays is the same as comparing their addresses. This means that ``++array1.equals(array2)++`` is equivalent to ``++array1==array2++``.

However, some developers might expect ``++Array.equals(Object obj)++`` to do more than a simple memory address comparison, comparing for instance the size and content of the two arrays. Instead, the ``++==++`` operator or ``++Arrays.equals(array1, array2)++`` should always be used with arrays.

=== Noncompliant code example

[source,java]
----
interface KitchenTool { ... };
interface Plant {...}

public class Spatula implements KitchenTool { ... }
public class Tree implements Plant { ...}
//...

Spatula spatula = new Spatula();
KitchenTool tool = spatula;
KitchenTool [] tools = {tool};

Tree tree = new Tree();
Plant plant = tree;
Tree [] trees = {tree};


if (spatula.equals(tree)) { // Noncompliant; unrelated classes
  // ...
}
else if (spatula.equals(plant)) { // Noncompliant; unrelated class and interface
  // ...
}
else if (tool.equals(plant)) { // Noncompliant; unrelated interfaces
  // ...
}
else if (tool.equals(tools)) { // Noncompliant; array & non-array
  // ...
}
else if (trees.equals(tools)) { // Noncompliant; incompatible arrays
  // ...
}
else if (tree.equals(null)) { // Noncompliant
  // ...
}
----

== Resources

* https://wiki.sei.cmu.edu/confluence/x/5zdGBQ[CERT, EXP02-J.] - Do not use the Object.equals() method to compare two arrays

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

* Remove this call to "equals"; comparisons against null always return false.
* Remove this call to "equals"; comparisons between a type and an array always return false.
* Remove this call to "equals"; comparisons between an array and a type always return false.
* Use "Arrays.equals(array1, array2)" or the "==" operator instead of using the "Object.equals(Object obj)" method.


'''
== Comments And Links
(visible only on this page)

=== on 21 Nov 2024, 16:48:00 Alban Auzeill wrote:
[test-code-support-investigation-for-java] Decision for scope: Keep 'Main'. Silly equality comparisons are useful to fully tests "equals"".

include::../comments-and-links.adoc[]

endif::env-github,rspecator-view[]
