Looking at the Navigation Mesh library in the jME plugins there is a solution:
[java] FloatBuffer pb = mesh.getFloatBuffer(Type.Position);
IndexBuffer ib = mesh.getIndexBuffer();
// copy positions to float array
float[] positions = new float[pb.capacity()];
pb.clear();
pb.get(positions);
// generate int array of indices
int[] indices = new int[ib.size()];
for (int i = 0; i < indices.length; i++) {
indices = ib.get(i);
}[/java]
I had already seen this like 1-2 months ago, but I totally forgot, when I was looking into NavMesh generation and the NMGen