How we can isolate the variables a thread use?

[Shahram]

Hi I am using this code in order to run multiple treads. Among 30 thread created only tow of them fail due 
to NullPointerException. As it could be seen I pass ASEvaluator and aPopulation[i] to my Runnable via its 
contractor. I want to isolate these in each thread. The problem is when one thread change the value of one 
of these parameters other threads see the changes. 
Any idea?

package weka.attributeSelection;
 
 
public class antibodyEvaluator implements Runnable   {
 
	private Antibody antibodyToEvaluate;
	private SubsetEvaluator ASEval = new WrapperSubsetEval();
	private String threadName;
 
	public antibodyEvaluator(String name, SubsetEvaluator ASEvaluator, Antibody candidate)
	{
		this.threadName = name;
		this.ASEval = ASEvaluator;
		this.antibodyToEvaluate = candidate;
	}
 
	public void run()
	{
		try{
     		        antibodyToEvaluate.evaluate(ASEval);
			antibodyToEvaluate.setFitness(antibodyToEvaluate.getAffinity(0)+Math.abs(antibodyToEvaluate.getAffinity(1))+antibodyToEvaluate.getAffinity(3));
			System.out.printf("\n %s is successful.\n", threadName);
		} catch(NullPointerException ne)
		{
			System.out.printf("\nThread %s failed due to null pointer exception\n", this.threadName);
		}catch (Exception e) {
			// TODO Auto-generated catch block
			System.out.printf("\nError in evaluating %s.\n" + e.getMessage() , threadName);
		}
	}
 
	public Antibody getAntibody()
	{
		return antibodyToEvaluate;
	}
 
}
 
 
   private void evaluatePopulation (SubsetEvaluator ASEvaluator, Antibody [] aPopulation)
      throws Exception {
 
    	antibodyEvaluator[] evaluationTask = new antibodyEvaluator[aPopulation.length];
    	ExecutorService threadExecutor = Executors.newFixedThreadPool(2);
 
    	for (int i=0;i<aPopulation.length ;i++) {
    		  evaluationTask[i] = new antibodyEvaluator("ET"+Integer.toString(i), ASEvaluator, aPopulation[i]);
        	  threadExecutor.execute(evaluationTask[i]);
        }
 
   	  threadExecutor.shutdown();
 
	  //Wait until all threads finish
          while (!threadExecutor.isTerminated()) {}
 
      }

[Norm]

The problem is when one thread change the value of one of these parameters other threads see the changes.

Which variables are shared by the threads?
Why do the threads change the contents of the passed objects?
Can you clone the objects so each thread gets its own version.

Can you make a small simple program that compiles and executes to demonstrate your problem?

[copeg]

I want to isolate these in each thread.

What do you mean isolate? Do you mean you want each thread to have its own copy - so that one thread cannot change the values used by another? If so, you will have to deep copy/clone the objects.

Among 30 thread created

Why so many threads? In most cases, I'd guess you are loosing a lot of efficiency by creating so many threads.