why grant an outmost interface yield hashcode/equals hashmap?

with treemap it's excusable yield tradition comparator, so vital semantics presumption comparable objects total map. hashmaps however can't tranquil manner; functions providing crush values equivalence checks can't 'side-loaded'.

i think both easy useful settlement an interface retrofit hashmap (or new class)? something this, solely improved names:

  interface hasharator<t> {
    int alternativehashcode(t t);
    boolean alternativeequals(t t1, t t2);
  }

  category hasharatormap<k, v> {
    hasharatormap(hasharator<? super k> hasharator) { ... }
  }

  category hasharatorset<t> {
    hasharatorset(hasharator<? super t> hasharator) { ... }
  }

the problem gets excusable solution:

 new hasharatormap(string.case_insensitive_equality);

would doable, any component problems approach?

is proceed used any existent (non-jre) libs? (tried google, luck.)

edit: good workaround presented hazzen, nonetheless i'm fearful workaround i'm perplexing avoid... ;)

edit: altered due longer plead "comparator"; i think bit confusing.

edit: supposed answer union performance; adore some-more specific answer!

edit: there an implementation; supposed answer below.

edit: rephrased initial visualisation infer some-more clearly it's side-loading i'm after (and ordering; organization does go hashmap).