This is the part I currently need to work on for my own game..

What I've reasoned out so far is that I can have a CollisionBox on the GameObject which contains all the collision boundary information. Collisions are checked by GameObject.isColliding(other) - where the two CollisionBoxes compare whether they intersect.

if (gameObject.isColliding(other))
{
    gameObject.doCollision(other);
}

then the GameObject has a doCollision method which is overridden for various GameObjects

public GameObject
{
    CollisionBox collisionBox;
    CollisionType collisionType;
    
    public void doCollision(GameObject other)
    {
        switch(other.CollisionType)
        {
            case Inelastic: //etc
            case Elastic: //etc
            case Consumable: //(this one is for bullets, upgrades, pickups - 
                // things you collide with but the collision doesn't affect motion)
        }
    }
}

As you can maybe guess, CollisionType is an enum which is assigned to GameObject.

That was my initial plan anyway. Now I hope to take some inspiration from Collision detection and response in an Entity System - though I'll still probably end up with some type of "collisionType enum" to broadly group a type of collision.

This is the part I currently need to work on for my own game..

What I've reasoned out so far is that I can have a CollisionBox on the GameObject which contains all the collision boundary information. Collisions are checked by GameObject.isColliding(other) - where the two CollisionBoxes compare whether they intersect.

if (gameObject.isColliding(other))
{
    gameObject.doCollision(other);
}

then the GameObject has a doCollision method which is overridden for various GameObjects

public GameObject
{
    CollisionBox collisionBox;
    CollisionType collisionType;
    
    public void doCollision(GameObject other)
    {
        switch(other.CollisionType)
        {
            case Inelastic: //etc
            case Elastic: //etc
            case Consumable: //(this one is for bullets, upgrades, pickups - 
                // things you collide with but the collision doesn't affect motion)
        }
    }
}

As you can maybe guess, CollisionType is an enum which is assigned to GameObject.

That was my initial plan anyway. Now I hope to take some inspiration from Collision detection and response in an Entity System - though I'll still probably end up with some type of "collisionType enum" to broadly group a type of collision.