Why ClassPool is a class and not a interface? about javassist

[chibash]

I don't. So the variability is implemented out of the ClassPool object.
Making it an interface is just one option to support variability.

[publicocean0]

I wished to realize a pool using ehcache ... so memory can not overcome a limit .... but can use it also for a huge number of classes created on the fly.....
A simple solution seemed to override variable classes in ClassPool with new Map .... but variable i not defined as Map but Hashtable.
Finally i find a solution but it is not so elegant .... saving class bytecode externally in the ehcache and a different classloader for every call

[LunNova]

It would be nice if it was an interface, but at this point it would be a breaking change - many people will be relying on creating new ClassPool(). Maybe for the next major version?

You can always just extend ClassPool like this: https://github.com/nallar/ModPatcher/blob/master/src/main/java/javassist/ClassLoaderPool.java

Not ideal, as you need to put it in the javassist package for access to many things, but sometimes it's the only option.

[LunNova]

@publicocean0
For the Hashtable issue, you could either override all the methods in ClassPool that use the Hashtable, or if that's not feasible you can extend Hashtable and override every method in it to delegate to your cache. Not nice either, but it works.