I think I had a similar problem with one the Hemesh library examples here is how I got round it . I commented out the package in the included java file HEM_Noise.java, and fully specified the extends see below:-

//specifying package wblut.hemesh allows access to protected members of HE_Mesh and other elements
//package wblut.hemesh.modifiers;

import java.util.Iterator;

import wblut.hemesh.HE_Mesh;
import wblut.hemesh.HE_Selection;
import wblut.hemesh.HE_Vertex;
import wblut.geom.WB_Point;

public class HEM_Noise extends wblut.hemesh.modifiers.HEM_Modifier {

The P5SunflowAPIAPI library still works- the issue is with the SunflowAPIAPI (note the lack of P5!) which is pure Java. 

Thanks. It worked here for Sunflow.
I'm new to Processing and would like to ask if there is any more efficient GI renderer being used by now? (Instead of Sunflow)
I'm asking this because there is not seen much activity around Sunflow, whether in this forums or other places.

Besides, let's add that, in my case I also removed this part from my own code:

1. import com.briansteen.SunflowAPIAPI;

Thanks again.