Question

我收到这些错误。
收到IllegalArgumentException
在extractIndividualInstance Line 68收到错误在第33行我试图运行k最近邻算法
应该何时抛出IllegalArgumentException？我不明白如何使我的代码工作，一定是错的。

Error- 
Exception in thread "main" java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Unknown Source)
at Knn.extractIndividualInstance(Knn.java:68)
at Knn.main(Knn.java:33)

import java.util.*;

public class Knn {
public static final String PATH_TO_DATA_FILE = "coupious.data";
public static final int NUM_ATTRS = 9;
public static final int K = 262;

public static final int CATEGORY_INDEX = 0;
public static final int DISTANCE_INDEX = 1;
public static final int EXPIRATION_INDEX = 2;
public static final int HANDSET_INDEX = 3;
public static final int OFFER_INDEX = 4;
public static final int WSACTION_INDEX = 5;
public static final int NUM_RUNS = 1000;
public static double averageDistance = 0;

public static void main(String[] args) {
    ArrayList<Instance> instances = null;
    ArrayList<Neighbor> distances = null;
    ArrayList<Neighbor> neighbors = null;
    WSAction.Action classification = null;
    Instance classificationInstance = null;
    FileReader reader = null;
    int numRuns = 0, truePositives = 0, falsePositives = 0, falseNegatives = 0, trueNegatives = 0;
    double precision = 0, recall = 0, fMeasure = 0;

    falsePositives = 1;

    reader = new FileReader(PATH_TO_DATA_FILE);
    instances = reader.buildInstances();

    do {
        classificationInstance = extractIndividualInstance(instances);

        distances = calculateDistances(instances, classificationInstance);
        neighbors = getNearestNeighbors(distances);
        classification = determineMajority(neighbors);

        System.out.println("Gathering " + K + " nearest neighbors to:");
        printClassificationInstance(classificationInstance);

        printNeighbors(neighbors);
        System.out.println("\nExpected situation result for instance: " + classification.toString());

        if(classification.toString().equals(((WSAction)classificationInstance.getAttributes().get(WSACTION_INDEX)).getAction().toString())) {
            truePositives++;
        }
        else {
            falseNegatives++;
        }
        numRuns++;

        instances.add(classificationInstance);
    } while(numRuns < NUM_RUNS);

    precision = ((double)(truePositives / (double)(truePositives + falsePositives)));
    recall = ((double)(truePositives / (double)(truePositives + falseNegatives)));
    fMeasure = ((double)(precision * recall) / (double)(precision + recall));

    System.out.println("Precision: " + precision);
    System.out.println("Recall: " + recall);
    System.out.println("F-Measure: " + fMeasure);
    System.out.println("Average distance: " + (double)(averageDistance / (double)(NUM_RUNS * K)));
}

public static Instance extractIndividualInstance(ArrayList<Instance> instances) {
    Random generator = new Random(new Date().getTime());
    int random = generator.nextInt(instances.size() - 1);

    Instance singleInstance = instances.get(random);
    instances.remove(random);

    return singleInstance;
}

public static void printClassificationInstance(Instance classificationInstance) {
    for(Feature f : classificationInstance.getAttributes()) {
        System.out.print(f.getName() + ": ");
        if(f instanceof Category) {
            System.out.println(((Category)f).getCategory().toString());
        }
        else if(f instanceof Distance) {
            System.out.println(((Distance)f).getDistance().toString());
        }
        else if (f instanceof Expiration) {
            System.out.println(((Expiration)f).getExpiry().toString());
        }
        else if (f instanceof Handset) {
            System.out.print(((Handset)f).getOs().toString() + ", ");
            System.out.println(((Handset)f).getDevice().toString());
        }
        else if (f instanceof Offer) {
            System.out.println(((Offer)f).getOfferType().toString());
        }
        else if (f instanceof WSAction) {
            System.out.println(((WSAction)f).getAction().toString());
        }
    }
}

public static void printNeighbors(ArrayList<Neighbor> neighbors) {
    int i = 0;
    for(Neighbor neighbor : neighbors) {
        Instance instance = neighbor.getInstance();

        System.out.println("\nNeighbor " + (i + 1) + ", distance: " + neighbor.getDistance());
        i++;
        for(Feature f : instance.getAttributes()) {
            System.out.print(f.getName() + ": ");
            if(f instanceof Category) {
                System.out.println(((Category)f).getCategory().toString());
            }
            else if(f instanceof Distance) {
                System.out.println(((Distance)f).getDistance().toString());
            }
            else if (f instanceof Expiration) {
                System.out.println(((Expiration)f).getExpiry().toString());
            }
            else if (f instanceof Handset) {
                System.out.print(((Handset)f).getOs().toString() + ", ");
                System.out.println(((Handset)f).getDevice().toString());
            }
            else if (f instanceof Offer) {
                System.out.println(((Offer)f).getOfferType().toString());
            }
            else if (f instanceof WSAction) {
                System.out.println(((WSAction)f).getAction().toString());
            }
        }
    }
}

public static WSAction.Action determineMajority(ArrayList<Neighbor> neighbors) {
    int yea = 0, ney = 0;

    for(int i = 0; i < neighbors.size(); i++) {
        Neighbor neighbor = neighbors.get(i);
        Instance instance = neighbor.getInstance();
        if(instance.isRedeemed()) {
            yea++;
        }
        else {
            ney++;
        }
    }

    if(yea > ney) {
        return WSAction.Action.Redeem;
    }
    else {
        return WSAction.Action.Hit;
    }
}

public static ArrayList<Neighbor> getNearestNeighbors(ArrayList<Neighbor> distances) {
    ArrayList<Neighbor> neighbors = new ArrayList<Neighbor>();

    for(int i = 0; i < K; i++) {
        averageDistance += distances.get(i).getDistance();
        neighbors.add(distances.get(i));
    }

    return neighbors;
}

public static ArrayList<Neighbor> calculateDistances(ArrayList<Instance> instances, Instance singleInstance) {
    ArrayList<Neighbor> distances = new ArrayList<Neighbor>();
    Neighbor neighbor = null;
    int distance = 0;

    for(int i = 0; i < instances.size(); i++) {
        Instance instance = instances.get(i);
        distance = 0;
        neighbor = new Neighbor();

        // for each feature, go through and calculate the "distance"
        for(Feature f : instance.getAttributes()) {
            if(f instanceof Category) {
                Category.Categories cat = ((Category) f).getCategory();
                Category singleInstanceCat = (Category)singleInstance.getAttributes().get(CATEGORY_INDEX);
                distance += Math.pow((cat.ordinal() - singleInstanceCat.getCategory().ordinal()), 2);
            }
            else if(f instanceof Distance) {
                Distance.DistanceRange dist = ((Distance) f).getDistance();
                Distance singleInstanceDist = (Distance)singleInstance.getAttributes().get(DISTANCE_INDEX);
                distance += Math.pow((dist.ordinal() - singleInstanceDist.getDistance().ordinal()), 2);
            }
            else if (f instanceof Expiration) {
                Expiration.Expiry exp = ((Expiration) f).getExpiry();
                Expiration singleInstanceExp = (Expiration)singleInstance.getAttributes().get(EXPIRATION_INDEX);
                distance += Math.pow((exp.ordinal() - singleInstanceExp.getExpiry().ordinal()), 2);
            }
            else if (f instanceof Handset) {
                // there are two calculations needed here, one for device, one for OS
                Handset.Device device = ((Handset) f).getDevice();
                Handset singleInstanceDevice = (Handset)singleInstance.getAttributes().get(HANDSET_INDEX);
                distance += Math.pow((device.ordinal() - singleInstanceDevice.getDevice().ordinal()), 2);

                Handset.OS os = ((Handset) f).getOs();
                Handset singleInstanceOs = (Handset)singleInstance.getAttributes().get(HANDSET_INDEX);
                distance += Math.pow((os.ordinal() - singleInstanceOs.getOs().ordinal()), 2);
            }
            else if (f instanceof Offer) {
                Offer.OfferType offer = ((Offer) f).getOfferType();
                Offer singleInstanceOffer = (Offer)singleInstance.getAttributes().get(OFFER_INDEX);
                distance += Math.pow((offer.ordinal() - singleInstanceOffer.getOfferType().ordinal()), 2);
            }
            else if (f instanceof WSAction) {
                WSAction.Action action = ((WSAction) f).getAction();
                WSAction singleInstanceAction = (WSAction)singleInstance.getAttributes().get(WSACTION_INDEX);
                distance += Math.pow((action.ordinal() - singleInstanceAction.getAction().ordinal()), 2);
            }
            else {
                System.out.println("Unknown category in distance calculation.  Exiting for debug: " + f);
                System.exit(1);
            }
        }
        neighbor.setDistance(distance);
        neighbor.setInstance(instance);

        distances.add(neighbor);
    }

    for (int i = 0; i < distances.size(); i++) {
        for (int j = 0; j < distances.size() - i - 1; j++) {
            if(distances.get(j).getDistance() > distances.get(j + 1).getDistance()) {
                Neighbor tempNeighbor = distances.get(j);
                distances.set(j, distances.get(j + 1));
                distances.set(j + 1, tempNeighbor);
            }
        }
    }

    return distances;
}

}

The complete code is here

Answer 1

首先：发布完整的堆栈跟踪。传递给extractIndividualInstance的列表为空时抛出异常。由于缺少buildInstances的实现，我无法说清楚，但我想你无法从文件中加载数据。

<error>收到IllegalArgumentException </error>

1 个答案: