Do you have examples? Most modern Java libraries I know (e.g. Guava) implement interfaces and heavily use composition.
The "inheritance based" things mostly got deprecated/replaced when Java 1.5 introduced generics and most libraries needed to be heavily changed anyways.
The Android API is fascinatingly anachronistic. I have been programming Java since 1.0.2, but only recently started working with Android. It's been like stepping through a portal back to a time when we had no idea how to structure software.
Sadly, many of the "older" programmers haven't learned any better. And sometimes it's a limitation of the language (eg, Java which doesn't allow default implementations in interfaces).
