Question

My program compiled fine. But the problems start when I try to run it.

jesvin@Jesvin-Technovia:~/dev/drools/sudoku$ java App 
Exception in thread "main" java.lang.NoClassDefFoundError: org/drools/planner/core/solution/Solution
Caused by: java.lang.ClassNotFoundException: org.drools.planner.core.solution.Solution
        at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: App. Program will exit.

I know that the interface Solution was correctly resolved in compile time.

Here is the offending class Sudoku that implements Solution:

package domain;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.drools.planner.api.domain.solution.PlanningEntityCollectionProperty;
import org.drools.planner.core.solution.Solution;
import org.drools.planner.core.score.SimpleScore;

public class Sudoku implements Solution<SimpleScore>{
...

And here is the App class that is supposed to use an instance of the Sudoku class

import java.util.ArrayList;
...

import org.drools.planner.config.XmlSolverConfigurer;
...

//solution too
import org.drools.planner.core.solution.Solution;

import solution.SudokuGenerator;
import domain.Sudoku;

public class App{
    public static void main(String[] args){
    SudokuGenerator sg = new SudokuGenerator();
    Solution sudoku = sg.createSudoku();
    Solver solver = createSolver();
    solver.setPlanningProblem(sudoku);
    solver.solve();

    Sudoku result = (Sudoku) solver.getBestSolution();
    result.displaySolution();
    }

    private static Solver createSolver(){
    XmlSolverConfigurer configurer = new XmlSolverConfigurer();
        configurer.configure("solver.xml");
        return configurer.buildSolver();
    }
}

Is it the result of me wrongly casting between Sudoku and Solution?

---

My classpath is set as:

declare -x CLASSPATH=".:/home/jesvin/dev/drools/sudoku/binaries"

Answer 1

As @GPRathour wrote above, you need to add the jars from drools planner to the classpath.

I guess /home/jesvin/dev/drools/sudoku/binaries is a directory. You need put jars there.
Some thing like…

declare -x CLASSPATH=".:/home/jesvin/dev/drools/sudoku/binaries/drools-planner-core.jar

A better approach will be to add jars in the command line via -classpath

java -classpath path/jar1;path/jar App

In a exception stack you should always check the ’caused by ‘ messages. In this your real exception was Caused by: java.lang.ClassNotFoundException: org.drools.planner.core.solution.Solution.

( Other thing to note– Use packages. Having classes in appropriate packages helps lot in reading code later.)