Problem on soot path.

[damorosodaragona]

package main;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import soot.MethodOrMethodContext;
import soot.PackManager;
import soot.Scene;
import soot.SceneTransformer;
import soot.SootClass;
import soot.SootMethod;
import soot.Transform;
import soot.jimple.toolkits.callgraph.CHATransformer;
import soot.jimple.toolkits.callgraph.CallGraph;
import soot.jimple.toolkits.callgraph.Targets;

public class CallGraphExample
{	
	public static void main(String[] args) {
	   List<String> argsList = new ArrayList<String>(Arrays.asList(args));
	   argsList.addAll(Arrays.asList(new String[]{
			   "-w",
			   "-main-class",
			   "testers.CallGraphs",//main-class
			   "testers.CallGraphs",//argument classes
			   "testers.A"			//
	   }));
	

	   PackManager.v().getPack("wjtp").add(new Transform("wjtp.myTrans", new SceneTransformer() {

		@Override
		protected void internalTransform(String phaseName, Map options) {
		       CHATransformer.v().transform();
                       SootClass a = Scene.v().getSootClass("testers.A");

		       SootMethod src = Scene.v().getMainClass().getMethodByName("doStuff");
		       CallGraph cg = Scene.v().getCallGraph();

		       Iterator<MethodOrMethodContext> targets = new Targets(cg.edgesOutOf(src));
		       while (targets.hasNext()) {
		           SootMethod tgt = (SootMethod)targets.next();
		           System.out.println(src + " may call " + tgt);
		       }
		}
		   
	   }));

           args = argsList.toArray(new String[0]);
           
           soot.Main.main(args);
	}
}

This is the code that i find on soot tutorials for Call Graphs, now when i try to run it in eclipse i have this error:
Soot started on Tue Jul 10 18:50:06 CEST 2018
soot.SootResolver$SootClassNotFoundException: couldn't find class: testers.CallGraphs (is your soot-class-path set properly?)
at soot.SootResolver.bringToHierarchyUnchecked(SootResolver.java:228)
at soot.SootResolver.bringToHierarchy(SootResolver.java:208)
at soot.SootResolver.bringToSignatures(SootResolver.java:266)
at soot.SootResolver.bringToBodies(SootResolver.java:311)
at soot.SootResolver.processResolveWorklist(SootResolver.java:163)
at soot.SootResolver.resolveClass(SootResolver.java:133)
at soot.Scene.loadClass(Scene.java:853)
at soot.Scene.loadClassAndSupport(Scene.java:839)
at soot.Scene.loadNecessaryClass(Scene.java:1569)
at soot.Scene.loadNecessaryClasses(Scene.java:1582)
at soot.Main.run(Main.java:250)
at soot.Main.main(Main.java:147)
at main.CallGraphExample.main(CallGraphExample.java:54)

Ouuups... something went wrong! Sorry about that.
Follow these steps to fix the problem:
1.) Are you sure you used the right command line?
Click here to double-check:
https://soot-build.cs.uni-paderborn.de/doc/sootoptions/

2.) Not sure whether it's a bug? Feel free to discuss
the issue on the Soot mailing list:
https://github.com/Sable/soot/wiki/Getting-help

3.) Sure it's a bug? Click this link to report it.
Please be as precise as possible when giving us
information on how to reproduce the problem. Thanks!
[...]

I can't understand how i must setting soot path to run it.. Can somebody explain to me?
In my eclipse project i have 2 packages, first named "Main" where there is "CallGraphExample.java" class (is the class shown above), and second named "testers" where there is "CallGraph.java" class.
The code of "CallGraphs.java" is:

package testers;

public class CallGraphs
{
	public static void main(String[] args) {
		doStuff();
	}
	
	public static void doStuff() {
		new A().foo();
	}
}

class A
{
	public void foo() {
		bar();
	}
	
	public void bar() {
	}
}

[Symbolk]

Yeah this is the offical example, but really outdated (2008).
The same problem also bothers me, did you solve it?