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I used the examination example of drools planner to create my own example. I renamed the classes und erased every rule except one. The application started and I could load my XML-File. When clicking the “solve”-Button an error occured:
pool-2-thread-1] ERROR swingui.SolverAndPersistenceFrame - Solving failed.
java.lang.NullPointerException: null
Could anybody give me hint to fix the problem? I don’t know what the error message means.
Thank you.
It was the entire error message!
The problem was the cloneSolution method. I forget to implement the method. So the solver could not find a solution because it has to clone my objects.
For everybody: Don’t forget to implement this method and to copy the score attribute. Without a score the won’t be a real solution.