Hi! So a while ago I realised you could make ArrayLists with no class associated. ArrayList sampleList = new ArrayList(); I am working on a simple 2d platformer at the moment and created a class that contains the gravity function and all the needed variables, which all the other gravity-affected …

Try this aPlayer = (playerClass) sampleList.get(i); What was the error message?

So I don’t have much time right now but I put that line in and it didn’t give me an error message. I’ll have to adjust my code later to see if it really works! One question though: What exactly does that do? Is it like “if sampleList(i) == playerClass get it else do nothing” or what?

In your code aPlayer if of type playerClass sampleList holds instances of type Object sampleList.get(i); returns an instance of type `Object’ A variable of type playerClass can not reference an instance of type Object so aPlayer = sampleList.get(i); fails In this code aPlayer = (playerCl…

Depending on what you want to do with the objects in the list, you can either inherit all your gravity objects from a common gravityObject class and cast to this when accessing members of the list. Or you create a common gravity object interface which exposes the gravity methods for all objects in t…

What’s an interface? :sweat_smile:

It’s like a contract a class must fulfill. If a class implements an interface, it must provide all the fields and methods defined in the interface. Make a quick search about “java interface” and you will find a lot resources. Happy coding :slight_smile:

[image] needfulthing: If a class implements an interface, it must provide all the fields and … Not the fields. Actually, any fields declared in an interface are implicitly public, static & final! :no_mouth:

@quark : [image] quark: the returned Object instance is cast to the type playerClass Can I ask the object which type it is? println(someObject.getType());

You can get any object to report the class it was instantiated from // Object hierarchy class A{ } class B extends A { } class C extends B { } // Declare 3 variables of type A A a,b,c; // Now instantiate an object from each class a = new A(); b = new B(); c = new C(); // Get each object to repor…

Multiple classes in an (undefined) ArrayList?

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Multiple classes in an (undefined) ArrayList?

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