Factory Pattern input param to getInstance method

I have a Factory class giving me handlers of DTO objects. I made my Factory non instantiable.

public class CommonAdapterFactory {

    // non instantiable 
    private CommonAdapterFactory() { }
}

Now I was wondering if there is a general rule about how to make getInstance method signature.. I've found several ways, but most commons are this ones:

Use Class

I won't need to update an enum or know String values previously, but AFAIK no switch is possible:

public static CommonAdapter getInstance(Class adapter) throws Exception {
    if (adapter.equals(String.class))
        return new StringAdapter();

    throw new Exception("Parsed AdapterSelector is not compatible with AdapterFactory");
}

Use String.

Allowing me to switch but using and mantaining hardcoded constants (¿maybe in a different class?)

private static final String STRING = "String";

public static CommonAdapter getInstance(String adapter) throws Exception {
    switch (adapter) {
    case STRING:
        return new StringAdapter();
    default:
        throw new Exception("Parsed AdapterSelector is not compatible with AdapterFactory");
    }
}

Use enum

Similar to String but IMHO maybe a cleaner way and not hardcoding any values.

public enum CommonAdapterSelector {
    STRING, 
    OTHER;
}

// use enum (switch possible) 
public static CommonAdapter getInstance(CommonAdapterSelector adapter) throws Exception {
    switch (adapter) {
    case STRING:
        return new StringAdapter();
    default:
        throw new Exception("Parsed AdapterSelector is not compatible with AdapterFactory");
    }
}

• Is there a standard?
• Some of this implementations can affect performance?
• Wich one is easier to mantain when more than 50 adapters can be created?