CODEWITHSUNDEEP
javainheritanceinstance
user1619397
user1619397

Reputation: 730

Best way to check whether the instance of parent class rather than child class?

If I have a class A and a child class B extended from A, and I have an instance bbb of B from somewhere, what would be the best to check the instance bbb is not actually of A.

What I can think are the following two. Which is better or anything better than both of them?

1) if(!((bbb instanceof A) && (bbb instance of B)))

2) if(bbb.getClass().getName()!=A.class.getName()){

Thanks

Upvotes: 0

Views: 3025

Answers (2)

jmmurillo
jmmurillo

Reputation: 193

Let's change A for Animal and B for Bird

I you already have an instance of Bird it can't possibly be a "raw" Animal. As Bird is a more specific type of Animal, JAVA won't let you directly assign a "raw" Animal into a Bird variable. If you meant the other way round (you have an Animal and you want to tell if it is actually a Bird) you can do it using

if ( bbb instanceof Bird) ...

In short, if your question is right, you can be sure you have a Bird without the need of checking anything.

Upvotes: 0

sp00m
sp00m

Reputation: 48837

bbb actually is an instance of A since B extends A, so your first solution won't work.

Comparing the classes directly should suit your needs:

if (!A.class.equals(bbb.getClass()))

You could also think differently:

A bbb = ...;
if (bbb instanceof B) {
    // bbb has been instantiated via B or one of B subclasses
} else {
    // bbb has been instantiated via A or one of A subclasses except B
}

Upvotes: 4

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