Newbie's Weka problem - Unhandled Exception

Question

I am a total newbie to the weka software and in addition a newbie to java syntax. As a school task we need to write a simple java code for direct usage of neural network classifiers. So I did that but I have troubles compiling in the line data source and line independecies below it says Unhandled Exception. I tried try catch, but it didnt work. What could be the problem and how can I solve it. Thank you in advance.

package ime; 
import weka.core.converters.ConverterUtils.DataSource;
import weka.core.Instances; 
import weka.classifiers.functions.MultilayerPerceptron;
import weka.classifiers.Evaluation;
import java.util.Random;

public class Wekaclass 
{
    public static void main(String [] args) 
    {
        DataSource source = new DataSource("iris.arff");
        Instances instances = source.getDataSet();
        instances.setClassIndex(instances.numAttributes() - 1);

        MultilayerPerceptron mlp = new MultilayerPerceptron();
        mlp.buildClassifier(instances);
        SerializationHelper.write("mlp.model", mlp);
        MultilayerPerceptron mmm = (MultilayerPerceptron)SerializationHelper.read("mlp.model");


        System.out.println("Done training.");
        System.out.println("Testing network...");

        Evaluation eval = nealuation(instances);
        eval.crossValidateModel(mlp, instances, 2, new Random(1));
    }

}