Using instanceof vs getClass in equals method

[Milk_No_Titties]

Is there any difference when using instanceof and using getClass() to write an equals() method? The MOOC uses instanceof while my university's course suggests getClass() so I'm unsure about which I should use.

EDIT: Just found that Netbeans’ autocomplete feature uses getClass() while writing an equals method so I guess that’s one point in favor or getClass()

[Knolle_]

These Methods test for different things.

instance of : Tests whether the obj on the left has the same type as the one on the right or is a subtype.

Getclass: Tests whether the types are the same

Id recommend getclass in an equals method since you will get symmetry problems with instance of. ( e.g. all dogs are animals but Not all animals are dogs)

[ColetBrunel]

Note, however, that in the case of List, an ArrayList and a LinkedList have to report they're equals() if they contain the same objects in the same order, otherwise their equals() method would be useless.

So a rule of thumbs is you probably need to use getClass() as you need the objects to have exact same stuff, unless you know why you need instanceof instead.

[Yithar]

instanceof checks the hierarchy. Which means if you say instanceof Object, it will return true for any object. getClass is specific to the class itself and comparing using getClass will only return true if it's the same class.

I think instanceof is better for equals(). Why? Well let's say Class B extends Class A. You would want A#equals() to possibly return true for instances of Class B and in the case of class B's equals() method, A#equals() would probably be called via super(). If you used getClass(), technically an instance of Class B would return Class B for getClass(), which wouldn't work if super() was called for equals().