REFLECTION: Getting the field from a class without the name

I want to get the java.lang.reflect.Field of (Eg. Object.field1), but my program is going to be obfuscated. I can't use the name of the field, but I just want to get it by that reference. I also don't want to cycle through the array of fields and find the one I want.

Sorry if I worded things wrong, I don't know what I'm supposed to call that.