Currently the method is implemented like

public List<Class<?>> parameterList() {
  return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
}

This seems to be excessive, as three objects are allocated here. Instead we can use List.of(ptypes) which doesn't allocate anything for empty array and for one of length 1 and 2 allocates lightweight objects with 1 and two fields respectively still copying longer arrays. This is likely to be fruitful as most of methods have 0-2 parameters.

Also there is a couple of cases when MethodType.parameterLis() is called to get its size, which is excessive either as we can use MethodType.parameterCount() instead.