classifier.java

这是一个用于测试用的搜索引擎的案例

package ir.classifiers;

import java.util.*;
import ir.vsr.*;

/**
 * Abstract class specifying the functionality of a classifier. Provides methods for 
 * training and testing a classifier
 *
 * @author       Sugato Basu and Yuk Wah Wong
 */

public abstract class Classifier {
     
    /** Used for breaking ties in argMax() */
    protected static Random random;

    /** Array of categories (classes) in the data  */
    protected String[] categories;

    static {
        random = new Random();
    }

    /** The name of a classifier 
    * @return the name of a particular classifier
    */
    public abstract String getName();
    
    /** Returns the categories (classes) in the data 
    * @return an array containing strings describing the categories
    */
    public String[] getCategories() {
	return categories;
    }

    /** Trains the classifier on the training examples 
    * @param trainingExamples a list of Example objects that will be used
    * for training the classifier */
    public abstract void train(List<Example> trainingExamples);
    
    /** Returns true if the predicted category of the test example matches the correct category,
	false otherwise */
    public abstract boolean test(Example testExample);

    /** Returns the array index with the maximum value 
     * @param results Array of doubles whose index with max value is to be found.
     * Ties are broken randomly. 
     */
    protected int argMax(double[] results){
	ArrayList<Integer> maxIndices = new ArrayList<Integer>();
	maxIndices.add(0);
	double max = results[0];
	
	for(int i=1; i<results.length; i++){
	    if(results[i]>max){
		max=results[i];
		maxIndices.clear();
		maxIndices.add(i);
	    } else if (results[i]==max) {
		maxIndices.add(i);
	    } 
	}
	int returnIndex;
	if (maxIndices.size() > 1) {
	    // break ties randomly
	    int winnerIdx = random.nextInt(maxIndices.size());
	    returnIndex = maxIndices.get(winnerIdx);
	} else {
	    returnIndex = maxIndices.get(0);
	}
	return(returnIndex);
    }
}