While I've never really found much practical use for mixins, it is fairly easy to create a runtime system for them in Java. Any interface can become a mixin sim

While I've never really found much practical use for mixins, it is fairly easy to create a runtime system for them in Java. Any interface can become a mixin simply by storing state in a static global hashmap with `this` as the key to the map. Specifically for the map, I would use `Collections.synchronizedMap(new WeakHashMap<>())` so that the map is thread-safe and allows mixin instances to be garbage collected.