Responder

/**
 * The responder class represents a response generator object.
 * It is used to generate an automatic response to an input string.
 *
 * @author Daffa Tristan Firdaus
 * @version 0.1 (05 November 2020)
 */

import java.util.*;
public class Responder
{
    private Random randomGenerator;
    private ArrayList<String> defaultResponses;
    private HashMap<String, String>responseMap;
    /**
     * Construct a Responder - nothing to do
     */
    public Responder()
    {
        randomGenerator = new Random();
        defaultResponses = new ArrayList<String>();
        responseMap = new HashMap<String, String>();
        fillResponses();
        fillDefaultResponses();
    }
    /**
     * Generate a response.
     * @return A string that should be displayed as the
     * response
     */
    public String generateResponse(HashSet<String> words)
    {
        for(String word:words)
        {
            String response = responseMap.get(word);
            if(response != null)
                {
                    return response;
                }
        }
        return pickDefaultResponse();
    }
    /**
     * Build up a list of default responses from which we can pick one
     * if we don't know what else to say.
     */
    private void fillResponses()
    {
        responseMap.put("hey", "Hello, How can i help you?");
        responseMap.put("hello", "Hi there! " + "How can i help?");
        responseMap.put("error", "I am sorry to hear that"
        + ", We are trying to fix the problem as soon as possible");
        responseMap.put("nice", "Thank you for your compliment");
        responseMap.put("issue", "I am sorry for your inconvenience"
        + ", What is the issue?");
        responseMap.put("thanks", "It's my pleasure!");
    }
    private void fillDefaultResponses()
    {
        defaultResponses.add("Sorry I can't understand.");
        defaultResponses.add("Please try again.");
    }
    private String pickDefaultResponse()
    {
        int index = randomGenerator.nextInt(defaultResponses.size());
        return defaultResponses.get(index);
    }
}