I don't see anything wrong with posted answers with new technology on old posts. Times change and what would have been good advice 2 or 3 years ago might not be the best advice to give today. It is also reasonable to assume that OP just might still be maintaining the code and should be alerted to new alternatives.

I think we should be careful about two things when adding new answers to old questions though.

1. It must be an acceptable Code Review answer. Meaning, it must be an actual code review. Neither of the answers referenced give a meaningful review. They offer alternative solutions without any explanation as to why the alternatives are better.
2. Answers providing solutions using new technology should probably disclaim themselves a little bit. "I know that Java 8 wasn't around when you posted this, but I think this new feature [x] would be perfect for this because [reasons]." This answer at least mentioned the new technology, but failed to mention that it is a new technology.

Stack Exchange is built to be a question and answer archive. Part of this paradigm is allowing new information and technologies to be taken into consideration long after the question was originally asked and answered. I would say that not allowing new answers goes against the spirit of Stack Exchange in general.

I don't see anything wrong with posted answers with new technology on old posts. Times change and what would have been good advice 2 or 3 years ago might not be the best advice to give today. It is also reasonable to assume that OP just might still be maintaining the code and should be alerted to new alternatives.

I think we should be careful about two things when adding new answers to old questions though.

1. It must be an acceptable Code Review answer. Meaning, it must be an actual code review. Neither of the answers referenced give a meaningful review. They offer alternative solutions without any explanation as to why the alternatives are better.
2. Answers providing solutions using new technology should probably disclaim themselves a little bit. "I know that Java 8 wasn't around when you posted this, but I think this new feature [x] would be perfect for this because [reasons]." This answer at least mentioned the new technology, but failed to mention that it is a new technology.

Stack Exchange is built to be a question and answer archive. Part of this paradigm is allowing new information and technologies to be taken into consideration long after the question was originally asked and answered. I would say that not allowing new answers goes against the spirit of Stack Exchange in general.