About the use of CacheWriter after it has been removed

[WeiMingzhi]

Hello,
I found during the upgrade from 2.x to 3.x that CacheWriter has been removed,
and the 2.x version has annotated 'Scheduled for removal in version 3.0.0. Consider instead using Map compute methods for extending manual write and remove operations, and using Caffeine.evictionListener(RemovalListener) for extending removals due to eviction.'.
I know how to use the listener when removing, and I don't see how to implement the extension of the put operation.
Please excuse my lack of technical skills, can you show a demo example, such as printing key and value when adding.
Or that this case is not suitable for using caffeine, it would be better to use map.put directly.
Thanks.

[ben-manes]

Hi @WeiMingzhi,

Cache<String, Integer> cache = Caffeine.newBuilder().build();
cache.asMap().compute("a", (key, oldValue) -> {
  int newValue = 1;
  System.out.printf("%s: %d => %d%n", key, oldValue, newValue);
  return newValue;
});
cache.asMap().compute("a", (key, oldValue) -> {
  int newValue = 2;
  System.out.printf("%s: %d => %d%n", key, oldValue, newValue);
  return newValue;
});
System.out.printf("Cache contains: %s%n", cache.asMap());

cache.asMap().compute("a", (key, oldValue) -> {
  System.out.printf("%s: %d => %d%n", key, oldValue, null);
  return null;
});
System.out.printf("Cache contains: %s%n", cache.asMap());

a: null => 1
a: 1 => 2
Cache contains: {a=2}
a: 2 => null
Cache contains: {}

I hope that helps clarify things. Please let me know if you have further questions.

[WeiMingzhi]

Thanks, @ben-manes
This usage still manipulates the Map every time and is not easy to use in a project.
However, the features I described are not required in use.
Thanks again for your reply!