CODEWITHSUNDEEP
classinterfacejava-8static-methods
Piyush Kothari
Piyush Kothari

Reputation: 61

Performance impact on Class Loading VS Interface Loading in Java 8

I want to create a common functionality across many classes. SO I have 2 approaches. 1) Create a new class and have a static method in it. 2) Create a new interface and have a concrete static method in it.

Can anyone explain the difference with respect to performance on both these approaches? Please consider both memory and processing impact.

Which approach should I choose and why?

Upvotes: 2

Views: 381

Answers (1)

Eugene
Eugene

Reputation: 120848

Performance wise it should not matter, meaning that even if it is, it would be extremely small; so this should never drive your decision.

On the other hand defining an interface with a static method that is solely used for common code is a big code smell IMO. static methods in interfaces are usually defined so that they return an instance of this interface; I tend to look at them as static factory methods that usually return instances of themselves, like Predicate#isEqual:

static <T> Predicate<T> isEqual(Object targetRef) {
    return (null == targetRef)
            ? Objects::isNull
            : object -> targetRef.equals(object);
}

Besides that an interface purpose is still to be extended, if you write a simple static method inside it, you are sort of breaking that rule.

Another problem is that when you define a static method in an interface, classes that extend this interface can not use that method. Unlike default methods for example. So if you have an interface:

interface Test {
    public static String test() {
        return "";
    }

    public default String testAgain() {
        return "";
    }
}

And a class TestImpl that extends this interface, than:

 TestImpl ti = new TestImpl();
 ti.testAgain();
 ti.test(); // will not compile

So may be you can use a default method instead of static. I sometimes favor this because it keeps the code closer to where I need it: if a certain class implements an interface with a default method - the code is right there, I don't need to use an external class.

static utility classes on the other hand are present all over the jdk for example, like Collections, Streams or Spliterators and that is what I would use if I were in your shoes.

Upvotes: 1

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