JBullet - Java port of Bullet Physics Library

Base library 
Package Description
com.bulletphysics
Contains global variables and callbacks.
com.bulletphysics.linearmath
Vector math library.
com.bulletphysics.linearmath.convexhull
Convex Hull library for converting point clouds to polygonal representation.
com.bulletphysics.util
Java-specific utility classes.
Collision library 
Package Description
com.bulletphysics.collision.broadphase
Broadphase collision code for fast determining of overlapping pairs.
com.bulletphysics.collision.dispatch
Dispatching code for collisions between various shapes.
com.bulletphysics.collision.narrowphase
Narrow-phase collision.
com.bulletphysics.collision.shapes
Collision shapes.
Dynamics library 
Package Description
com.bulletphysics.dynamics
DynamicsWorld and RigidBody.
com.bulletphysics.dynamics.character  
com.bulletphysics.dynamics.constraintsolver
Constraints and solvers.
com.bulletphysics.dynamics.vehicle  
Extras 
Package Description
com.bulletphysics.extras.gimpact
Provides support for moving concave triangle meshes.
Other Packages 
Package Description
com.bulletphysics.dom