CODEWITHSUNDEEP
javainstanceofcomparison-operators
travega
travega

Reputation: 8415

Java instanceof operator

Is there a valid class Type variable that can be used with the instanceof operator? For Example:

String s = "abc";

Class<?> classType = String.class;

if (s instanceof classType) {
    //do something
}

as an alternative to this:

if (s.getClass() == classType) {
    //do something
}

Would there be any performance benefit?

Upvotes: 2

Views: 25523

Answers (2)

Jeff Storey
Jeff Storey

Reputation: 57192

What you're doing is not actually the same. Consider what happens with subclasses (I know you can't subclass String, so in the String case it doesn't matter).

class A {}
class B extends A {}

B b = new B();
b instanceof A // true
b.getClass() == A.class // false

If you have an object and you want to know if it is an instanceof a certain type and you have the Class object, you can use the Class#isInstance method.

In either case, I expect performance differences to be insignificant.

Upvotes: 14

Steve B.
Steve B.

Reputation: 57284

There's also 

Class<?> classType = String.class;

if (classType.isInstance(s)) {...

As for performance, I'd expect the differences between any of these to be negligible.

Upvotes: 3

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