This is basically the same report as MCPE-58748 but for Java Edition since I couldn't find one.

Bees just disappear extremely quickly. I had one bee to begin with, which disappeared after a couple game days. Later I got a bee nest with 3 bees from an oak tree near my base. I bred two of them (for a total of 3 adult bees and 1 baby bee) and soon thereafter two of them seemed to have already disappeared again. So I bred the remaining two bees (for a total of 2 adult bees and 1 baby bee) and went off to do other duties. When I came back it seemed I had lost two bees again (yes, I checked the hives by standing next to them for a minute to listen for any sounds, and there were none).

A while later I was out harvesting my wheat and I spotted an adult bee and a baby bee flying together (see below for screenshot). It seemed pretty far away from the hives, but I thought (hoped) that they were doing their thing and they would return to their hive later.

After returning from a caving adventure I checked the hives and they were still not ready to harvest (the last time I harvested them was a long time ago). I went looking around for the bees and couldn't find a single one. I waited a while (several game days) and the hives still look abandoned. No bees to be seen anywhere. So it's safe to say my last two bees vanished as well.

A quick reddit search shows that I'm not the only one who's had this problem - there are complaints of disappearing bees from as far back as 7 months ago and as recent as 2 days ago.

I read a couple dozen of those posts and the theme seems to be that bees are happily suiciding on water, fire, cacti. I have not witnessed this happening with my bees but it seems plausible since I do have a natural waterfall near my base (around which I've arranged my crops), and an elevated campfire (for making it easier to spot my base from a distance).

There were also one or two comments saying that bees may randomly fly up and up without stopping, or otherwise randomly abandon their beehive/nest-based "neighborhood". Another commenter suggested that bees may also be entering solid blocks and suffocating inside, which has been a long-standing issue with animals that I know very well (although haven't observed recently).

Another type of comment suggested that maybe the bees could be attacking me and dying that way without me noticing. I can assure you that the few times I harvested honey from the hives I was very careful, attentive, and made sure that no bees were in or near the hives, and I would have surely noticed a bee stinging me. This hypothesis can be ruled out.

I'm making this report because I was actually pretty disappointed to lose all my bees, because I enjoyed this new feature surprisingly much, I was looking forward to having bees flying around outside my base and pollinating my crops, listening to the cute buzzing sounds they make when I'm harvesting... but it seems I can't have that. Apparently the only way to maintain a bee culture is to have them completely enclosed in a sanitized space. I'm not completely against that, I just don't have the materials or the motivation to build something like that right now.

I think that open-air bee farms should be viable. I think it's something to be expected by many players. Why not?

I remember that you have fixed suiciding behavior with other animals before.

So please, fix this (whatever the actual cause is - suiciding or wandering off). Make their AI smarter, or lock down their wandering. It shouldn't be hard for you to diagnose. I have attached a screenshot of my base. It's nothing unusual. Just a pretty natural environment. I've got chickens and sheep too - they're fine.

The two beehives are next to the base entrance, near the top of the stone brick staircase.

The place where I last saw that adult & baby bee is a bit left of the waterfall - which is well past 20 blocks away from the hives (20 blocks is supposed to be the maximum wander distance according to this 20w12a snapshot summary video I watched recently).

The seed is: 4500432789051034519

(The world origin is very close to where my base is. Just look for the waterfall.)

World type: AMPLIFIED

All other options are default.

No mods.