Modifying platform/frameworks/base package

I'm planning to开发者_如何学C modify some bits in the platform/frameworks/base project in Android Donut r2. The modifications are very small and goes into java packages android.graphics and android.text (the API isn't affected).

What jar libraries do I have to copy from the recompiled platform? the modifications are small and I don't want to replace the whole system.. I'm trying to replace specific jar libraries.

Not sure how many 'bits' need modifying, but perhaps you could just try to extend the classes you need?