Correctly identifying a Fixture from an extended class in Box2D's ContactListener

Sorry for the confusing title, I dont know how to resume it that much.

Im making a game, and I have a simple class Mob which is extended by Warrior and Enemy.

A Mob has a Body, and that body usually has one main Fixture.

Im setting the Body’s userdata to the class object (Warrior’s Body has a pointer to Warrior in its UserData) and im setting the Fixture’s userdata to a String which identifies what the fixture is. For example, the Warrior’s Body’s Fixture has the String “warrior” in its UserData.

The problem is, when a contact happens, i have common logic for a Mob, and i have specific logic for Warrior and Enemy.

Still, I cant find a good way to identify the collided fixtures at such a level.

For example, say I have these methods for code readability, since a Contact’s Fixture order is hard to guess and I dislike writing the same code for both Fixtures:

public boolean isPartOfContact(Contact c, String userdata)
{
    return (c.getFixtureA().getUserData().equals(userdata) ||
            c.getFixtureB().getUserData().equals(userdata));
}

public Fixture extractFixture(Contact c, String userdata)
{
    if(c.getFixtureA().getUserData().equals(userdata))
        return c.getFixtureA();

    if(c.getFixtureB().getUserData().equals(userdata))
        return c.getFixtureB();

    return null;
}

public Body extractBody(Contact c, String userdata)
{
    return extractFixture(c, userdata).getBody();
}

With these, I can write something like:

    if(isPartOfContact(contact, "warrior"))
    {
        if(isPartOfContact(contact, "map")) //warrior vs terrain
        {
            //Get warrior object
            ServerWarrior warrior = (ServerWarrior) extractBody(contact, "warrior").getUserData();
            //...
        }
    }

But what if I want to check for mob? warrior’s userdata is “warrior” and enemy’s userdata is “enemy”. Unless I check for class instances I cant think of a smart way of identifying them correctly.

I realise this really looks like fancy details which shouldnt really matter so soon in development but Im curious about how to create a Box2D ContactListener in a way which doesnt seem “hacked”.