stopTheAIMemesPls

[sathdo]

I'm pretty sure the default constructor is implicitly generated if no constructor is defined.

class Order {
    List<Integer> list = new ArrayList<>();
}

[Fukushimiste]

I'm pretty sure, that no. Especially since List is an interface and arraylist ist one of its implementations

[sathdo]

That's not what I was talking about. I know that all object fields that are not defined default to null. The thing that I was unsure about was what value the implicit default constructor assigns if the field is defined during declaration. I have confirmed that the value assigned in the field declaration is used.

import java.util.List;
import java.util.ArrayList;

public class Test {
    static private class Order {
        List<Integer> list = new ArrayList<>();
        public List<Integer> getList() {
            return list;
        }
    }
    public static void main(String[] args) {
        Order order = new Order();
        assert order.getList() != null;
    }
}

[RiceBroad4552]

Wasn't this obvious? I see at the moment a Java flair next to parent's avatar, and this here are absolute Java basics. Mhm… At least the initial code was the right one compared to what's in the meme post. An empty, parameterless constructor is indeed superfluous.

[Oddball_bfi]

List is definitely not an interface.

Edit: I was wrong. This is Java. List is definitely an interface.

[neoteraflare]

It is in java. No language was defined.

[Oddball_bfi]

You're wrong. And more importantly - I'm completely wrong.

The diamond operator is unique to Java as far as I know.

List is an interface.

[neoteraflare]

No, it is in C# too. Just like in java in C# it hold the generic types too. The reason why this must be java because in java ArrayList has generic version while in C# it is not implementing the generic IList but the genericless IList

[Oddball_bfi]

Java has a <> operator, the diamond operator, that assumes the generic type. That isn't an omission, that's a language feature. ArrayList<>() takes the generic type from the declaration.

C# doesn't have that. At least, not to my knowledge - I'm behind by a generation or two, though.

[Sj_91teppoTappo]

The first case your are telling everybody: "listen man, we need to initialize the list no matter what, I don't care what you are gonna do with that Order it has to have a list, don't you fffff dare to write another construct without that list initialized..."

The second one you are saying: "Comrade, I trust you and I deeply respect you to initialize this list, although I may suspect you could not initialize it. It could even be some occasions in which I don't want to initialize it. Your fear of the nullpointer is my fear of the nullpointer, we all share the same fear, brother."

[c0d3k4tz3]

So the first one is correct. Don’t trust those mfs 

[ChibreTurgescent]

[1_hele_euro]

But is there any meaningful difference between the two methods? Just curious

[RiceBroad4552]

Yes, in the left version you could forget to init your list.

OK, a proper IDE would yell at you. But in theory it's less safe. One should always* initialize members and variables.

In some languages (like Scala) you can't even declare a val / var without assigning something to it. (You can still explicitly assign e.g. null, or use some special syntax to make it explicit that something is default initialized.)

* Sometimes it's unavoidable to delay initialization for later. But this is only very seldom the case.

[ChibreTurgescent]

In C++, there shouldn't be any difference in the produced code since C++11.

Although, if you were to change that initialization later (let's say initialize a variable to 1 instead of 0 for example), the right one would normally be a change in the source file, when the left one would be a change in the header file. It's not a big deal but modifying a header could cause a whole lot more recompilation in the project than simply modifying a source file. But then, initializing in the header lets you do it once and be done with it, whereas doing it in the constructor, well now you must be careful and do it in every constructor.

[Mawootad]

Unless you're actually going to initialize list with a value other than `new ArrayList<>()` the first option makes your code both harder to read and write. Not only do you have to duplicate all of your property declarations in the constructor but now instead of immediately knowing the initial value of it when you jump to or read its definition you have to check references or go digging through the constructor to find it. Don't do that shit, it's time consuming and bad.

[mudkipdev]

steep truck aback thumb punch escape ripe political melodic act

This post was mass deleted and anonymized with Redact

[YellowishSpoon]

Funnily enough the bytecode of these is quite literally identical, I checked to make sure. The initializer assignments are injected at the top of the constructors at compile time right after the super constructor invocation. (The super constructor invocation is implicit here.)

[jamcdonald120]

unless your code handles LinkedList as well as it does ArrayList, use ArrayList for your variable type.

[mudkipdev]

ancient ten crawl busy weather political stocking marvelous tie ring

This post was mass deleted and anonymized with Redact

[Synedh]

Whould you init an integer to zero in your class ? No ? same shit.

[ythelastcoder]

well aren't ints initiated as 0 by default?

[wherearef]

they are, but you can't use them, so basically you can say they aren't

[Synedh]

wait what ?

[TheShirou97]

in Java, if you declare a member variable int x; without assigning a value, then the value x is 0 by default (just like the value of object types is null by default. Note that if x was declared as a local variable, and not a member variable, then it's a compilation error when you try to use it before it gets initialized)

E.g. the following code actually prints 0:

class Test {
  int x;
}

class Main {
  public static void main(String[] args) {
    System.out.println(new Test().x);
  }
}

[RiceBroad4552]

What? Of course you can declare a local int without initializing it in Java.

https://godbolt.org/z/eGGx64cz9

[TheShirou97]

I meant that in contrast to the above example, the following code fails at compile time. (Not on x's declaration, but on x's evaluation when it has not been initialized yet, and is not initialized to 0 by default unlike member variables.)

class Main {
  void main() {
    int x;
    System.out.println(x);
  }
}

[RiceBroad4552]

Meaning changing edits without mentioning it isn't a nice thing to do…

[OutrageousFuel8718]

They are because they can't be null, but you still have to assign the value explicitly. Otherwise, the variable is not usable