Are class methods duplicated a million times if I have a million instances?

Question

Let's say I have this code:

class A {
  void f(){
    // ... some long function code
  }
}
for (int i = 0; i < 1000000; i++) {
  A a = new A();
}

My question is: will the function if be replicated a million times in memory in this case? If so, does it make sense to use static methods?

I think it answers the question: https://stackoverflow.com/a/6606490/2956272. — , Sep 25 '19 at 06:03
Depends on the context. If you have something that is same across all object then yes. Make that method static though I doubt that methods take memory space. — Yoshikage Kira, Sep 25 '19 at 06:03

Amit Bera · Accepted Answer · 2019-09-25T06:06:20.647

4

Why do you think the method f() needs to be replicated million times? The method is nothing but a set of reusable instructions group in a single namespace. The definition of method will get it from the Byte code at the run time easily. So, JVM does not need to copy the definition of method in each and every Object created as it does not need to do so and it is true for each type of method static, nonstatic.

edited Sep 25 '19 at 06:06

answered Sep 25 '19 at 06:02

Amit Bera

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The question would have made more sense if op was asking about variables. – Yoshikage Kira Sep 25 '19 at 06:06
@Goion Yes, it makes more sense if a question is about variable/properties. – Amit Bera Sep 25 '19 at 06:08
Thank you, now I got a clear and simple answer to a simple quesiton. I don't understand why people downvoted me – Moshe Shaham Sep 25 '19 at 06:39

score 0 · Answer 2 · answered Sep 25 '19 at 06:03

It always depends.

Sometimes method relies on properties of a object, so on every object such method would behave differently.

On the other hand, static method must be independent of object non-static properties, so it can be called without instantiating object.

It depends what you want to achieve.

Example: let's say you have a class User and you'd like to get age of object of that class. Would it make sense to have common static method? No, as every user would have different age.

On the other hand, you'd like to have method to get the type of person, something like "I am user" - this would be independent from the state (properties) of an object, so you could make this method static.

Are class methods duplicated a million times if I have a million instances?

2 Answers2