Signifies that a public API (public class, method or field) is subject to incompatible changes,
or even removal, in a future release. An API bearing this annotation is exempt from any
compatibility guarantees made by its containing library. Note that the presence of this
annotation implies nothing about the quality or performance of the API in question, only the fact
that it is not "API-frozen."
It is generally safe for applications to depend on beta APIs, at the cost of some extra
work during upgrades. However it is generally inadvisable for libraries (which get
included on users' CLASSPATHs, outside the library developers' control) to do so.