How do I properly inherit classes and structure my program?

I’m writing something for a project. I have various world objects (actual objects in the game — such as ore, trees, etc.) and they all have their respective areas. Copper ore has have a list of areas while iron ore has another list of areas.

For a while, I separated Ore, Trees, etc into their own classes. However, I came to the realization that they shared a lot of functionality and are all essentially world objects.

For example, I may look up the ore or tree which is the closest to the players level. I may look up the closest Copper ore to me, or the closest Oak tree to me.

In each separate class, I had a function that did those exact things. I realized I wasn’t taking advantage of OOP at all.

My question is: how would you design and structure something like this?

Would there be a WorldObject class that the other classes extend from?

Areas are statically defined by me. How would I attach an area to the object Copper in the ore class? Would I use a separate LookUpTable class to store information, ie a hashmap? Would area be it’s own class and would the WorldObject class inherit it?

I’m just not understanding how to apply the principles of OOP in this scenario, specially as a novice. Thanks.

Taking each of your questions:

1. How would you design and structure something like this?

2. Would there be a WorldObject class that the other classes extend from?

You can use super classes for a WorldObject which is then extended by your object classes:

public abstract class WorldObject { // Superclass
    // Private methods common to all world objects
    private int posx;
    private int posy;
    
    // Public methods common to all world objects
    public double distance(int x, int y);
}

public class Tree extends WorldObject { 
    // Inherited Methods
}

public class Ore extends WorldObject { 
    // Inherited Methods
}

3. Areas are statically defined by me.

I am not sure what you mean by "area"? I am assuming it is the position of the object, which you can certainly create:

public class Position {
    private int x;
    private int y;
    private int z; // if needed
    // Contructor, getters and setters
}

4A. Copper Ore?

If "Copper Ore" has "special" properties compared to other "ores", then create it as a new class that extends from WorldObject, or Ore class. If it just has different properties, then add those properties to Ore class:

public class Ore extends WorldObject { 
    private String type; // which may be "Copper", "Iron", etc.
    private double weight; // ....etc.

    // Inherited Methods
}

4B. How would I attach an area to the object Copper in the ore class? Would I use a separate LookUpTable class to store information, ie a hashmap?

Use a list of World Objects, where each has a position:

public List<WorldObject> objects = new ArrayList<>();

You don't really need to use a Map in your case. Maps are generally useful in ID, OBJECT relationships, where you can continuously sort and quickly find the object you need.

5. Would area be it’s own class and would the WorldObject class inherit it?

Again, I need more information on what "area" is. Though, if it is just position, you can include it as a field in WorldObject.

If I were you I would not go for inheritance, since it may bring you several limitation later on. For instance you cannot have multiple parent object in java and if you want to extend another class what would you do?

However, in such cases you can design your hierarchical inheritance to solve such case.But that is not always (easily and effortlessly) possible.

My solution is : prefer interface over inheritance. you can define world interface and all real world objects must implement it.