How to integrate muJava(μJava) with Weka source code to do mutation testing?

I'm trying to use muJava (a mutation system for Java programs) to do mutation testing for the implementations of SimpleKmeans algorithm in Weka3.8 source code.

I've already done some mutation testing on my own simple code. However, I met some problems when I'm trying to integrate it with Weka source code. I directly put the four subdirectories of muJava needed in the Eclipse project. And the 'scr' folder contains all the .java files in Weka source code. 'classes' folder contains the complied .class files of related .java files. Here is the problem I met in the console:

File G:\EclipseWS\wekaAuto\src\weka\clusterers\SimpleKMeans.java
[OJException] weka\clusterers\SimpleKMeans.java mujava.OpenJavaException:  
can't generate parse tree
All files are handled

The following error was showed when I only picked out the SimpleKMeans.java file.

File G:\EclipseWS\wekaAuto\src\SimpleKMeans.java
[OJException] SimpleKMeans.java mujava.OpenJavaException:  can't generate 
parse tree
All files are handled

Can anyone who are familiar with muJava to help me configure it in Weka source code? Or are there any other techniques to do mutation testing in Java?

Useful links: muJava-https://cs.gmu.edu/~offutt/mujava/

Weka -https://www.cs.waikato.ac.nz/ml/weka/documentation.html