Added ability to generate 1, 2, 3-gram models on a company/date-range basis using <UNK> to represent the initial appearance of a previously unknown word.

AppContext.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:aop="http://www.springframework.org/schema/aop"
+	xmlns:context="http://www.springframework.org/schema/context"
+	xsi:schemaLocation="http://www.springframework.org/schema/beans
+           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
+           http://www.springframework.org/schema/aop
+           http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
+           http://www.springframework.org/schema/context
+           http://www.springframework.org/schema/context/spring-context-2.5.xsd"
+    default-autowire="byName">
+
+	<bean id="dmdataSource"
+		class="org.springframework.jdbc.datasource.DriverManagerDataSource">
+		<property name="driverClassName" value="com.mysql.jdbc.Driver" />
+		<property name="url" value="jdbc:mysql://woodyfolsom.net:3306/cs6601p3" />
+		<property name="username" value="cs6601" />
+		<property name="password" value="n0nst@p" />
+	</bean>
+
+    <bean id="mySQLHeadlineSvc" class="net.woodyfolsom.cs6601.p3.svc.MySQLHeadlineServiceImpl" />
+	<bean id="yahooHeadlineSvc" class="net.woodyfolsom.cs6601.p3.svc.YahooHeadlineServiceImpl" />
+
+    <context:annotation-config /> 
+    <context:component-scan base-package="net.woodyfolsom.cs6601.p3"/>
+   
+</beans>

src/net/woodyfolsom/cs6601/p3/ModelGenerator.java

@@ -0,0 +1,115 @@
+package net.woodyfolsom.cs6601.p3;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.text.DateFormat;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.support.FileSystemXmlApplicationContext;
+import org.springframework.stereotype.Component;
+
+import net.woodyfolsom.cs6601.p3.domain.Company;
+import net.woodyfolsom.cs6601.p3.domain.Headline;
+import net.woodyfolsom.cs6601.p3.ngram.NGramModel;
+import net.woodyfolsom.cs6601.p3.svc.HeadlineService;
+
+@Component
+public class ModelGenerator {
+	private static final File stockSymbolsCSV = new File("stock_symbols.csv");
+
+	private static final int INVALID_DATE = 1;
+	private static final int IO_EXCEPTION = 2;
+	private static final int STOCK_SYMBOL_CSV_NOT_FOUND = 3;
+
+	@Autowired
+	HeadlineService mySQLHeadlineServiceImpl;
+
+	private NGramModel ngramModel = new NGramModel();
+	
+	public static void main(String... args) {
+
+		ApplicationContext context = new FileSystemXmlApplicationContext(
+				new String[] { "AppContext.xml" });
+		ModelGenerator modelGenerator = context.getBean(ModelGenerator.class);
+		DateFormat dateFmt = new SimpleDateFormat("yyyy-MM-dd");
+		
+		Date startDate = null;
+		Date endDate = null;
+		Date valStart = null;
+		Date valEnd = null;
+		try {
+			startDate = dateFmt.parse("2012-01-01");
+			endDate = dateFmt.parse("2012-03-31");
+			valStart = dateFmt.parse("2012-04-01");
+			valEnd = dateFmt.parse("2012-04-14");
+		} catch (ParseException pe) {
+			System.exit(INVALID_DATE);
+		}
+		
+		try {
+			List<Company> fortune50 = modelGenerator
+					.getFortune50(stockSymbolsCSV);
+			for (Company company : fortune50) {
+				System.out.println("Getting headlines for Fortune 50 company #"
+						+ company.getId() + " (" + company.getName() + ")...");
+				List<Headline> trainingSet = modelGenerator.mySQLHeadlineServiceImpl.getHeadlines(company.getStockSymbol(), startDate, endDate);
+				System.out.println("Pulled " + trainingSet.size() + " headlines for "
+						+ company.getStockSymbol() + " from " + startDate + " to " + endDate);
+				List<Headline> validationSet = modelGenerator.mySQLHeadlineServiceImpl.getHeadlines(company.getStockSymbol(), valStart, valEnd);
+				
+				if (trainingSet.size() == 0) {
+					System.out.println("Training dataset contains 0 headlines for " + company.getName() + ", skipping model generation.");
+					continue;
+				}
+				if (validationSet.size() == 0) {
+					System.out.println("Validation dataset contains 0 headlines for " + company.getName() + ", skipping model generation.");
+					continue;
+				}
+				
+				modelGenerator.ngramModel.reportModel(trainingSet, validationSet);
+				System.out.println("Finished " + company.getId() + " / 50");
+			}
+		} catch (FileNotFoundException fnfe) {
+			System.out.println("Stock symbol CSV file does not exist: "
+					+ stockSymbolsCSV);
+			System.exit(STOCK_SYMBOL_CSV_NOT_FOUND);
+		} catch (IOException ioe) {
+			System.out.println("Stock symbol CSV file does not exist: "
+					+ stockSymbolsCSV);
+			System.exit(IO_EXCEPTION);
+		}
+	}
+
+	private List<Company> getFortune50(File csvFile)
+			throws FileNotFoundException, IOException {
+		List<Company> fortune50 = new ArrayList<Company>();
+		FileInputStream fis = new FileInputStream(csvFile);
+		InputStreamReader reader = new InputStreamReader(fis);
+		BufferedReader buf = new BufferedReader(reader);
+		String csvline = null;
+		while ((csvline = buf.readLine()) != null) {
+			if (csvline.length() == 0) {
+				continue;
+			}
+			String[] fields = csvline.split(",");
+			if (fields.length != 3) {
+				throw new RuntimeException(
+						"Badly formatted csv file name (3 values expected): "
+								+ csvline);
+			}
+			int id = Integer.valueOf(fields[0]);
+			fortune50.add(new Company(id, fields[1], fields[2]));
+		}
+		return fortune50;
+	}
+}

src/net/woodyfolsom/cs6601/p3/dao/HeadlineDao.java

@@ -13,4 +13,5 @@ public interface HeadlineDao {
 	
 	Headline select(int id);
 	List<Headline> select(String stock, Date date);
+	List<Headline> select(String stock, Date startDate, Date endDate);
 }

src/net/woodyfolsom/cs6601/p3/dao/HeadlineDaoImpl.java

@@ -24,7 +24,8 @@ public class HeadlineDaoImpl implements HeadlineDao {
 	
 	private static final String SELECT_BY_ID_QRY = "SELECT * from headlines WHERE id = ?";
 	private static final String SELECT_BY_STOCK_QRY = "SELECT * from headlines WHERE stock = ? AND date = ?";
-
+	private static final String SELECT_BY_DATE_RANGE_QRY = "SELECT * from headlines WHERE stock = ? AND date >= ? AND date <= ?";
+	
 	private JdbcTemplate jdbcTemplate;
 	
 	public int deleteById(int headlineId) {
@@ -66,6 +67,11 @@ public class HeadlineDaoImpl implements HeadlineDao {
 				new RequestMapper(), stock, date);
 	}
 	
+	public List<Headline> select(String stock, Date startDate, Date endDate) {
+		return jdbcTemplate.query(SELECT_BY_DATE_RANGE_QRY,
+				new RequestMapper(), stock, startDate, endDate);
+	}
+	
 	@Autowired
 	public void createTemplate(DataSource dataSource) {
 		this.jdbcTemplate = new JdbcTemplate(dataSource);

src/net/woodyfolsom/cs6601/p3/ngram/NGram.java

@@ -0,0 +1,95 @@
+package net.woodyfolsom.cs6601.p3.ngram;
+
+import java.util.LinkedList;
+
+public class NGram extends LinkedList<String> implements Comparable<NGram> {
+	private static final long serialVersionUID = 1L;
+	private int maxLength;
+
+	public NGram(int maxLength) {
+		super();
+		this.maxLength = maxLength;
+	}
+
+	@Override
+	public boolean add(String word) {
+		if (super.size() == maxLength) {
+			super.remove(0);
+		}
+		return super.add(word);
+	}
+
+	public int compareTo(NGram other) {
+		return this.toString().compareTo(other.toString());
+	}
+
+	public NGram copy() {
+		NGram nGram = new NGram(this.maxLength);
+		for (String token : this) {
+			nGram.add(token);
+		}
+		return nGram;
+	}
+
+	public NGram copy(int length) {
+		if (length > super.size()) {
+			throw new IllegalArgumentException();
+		}
+
+		NGram nGramCopy = new NGram(length);
+
+		for (int i = super.size() - length; i < size(); i++) {
+			nGramCopy.add(super.get(i));
+		}
+
+		return nGramCopy;
+	}
+
+	public boolean startsWith(NGram other) {
+		if (other.size() != this.size() - 1) {
+			return false;
+		}
+		for (int i = 0; i < other.size(); i++) {
+			if (other.get(i).equals(this.get(i)) == false) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	public NGram subNGram(int index) {
+		if (index > super.size()) {
+			throw new IllegalArgumentException();
+		}
+		NGram subNGram = new NGram(maxLength);
+		for (int i = index; i < super.size(); i++) {
+			subNGram.add(super.get(i));
+		}
+		return subNGram;
+	}
+
+	public NGram subNGram(int start, int end) {
+		if (start > end) {
+			throw new IllegalArgumentException();
+		}
+		NGram subNGram = new NGram(end - start);
+		for (int i = start; i < end; i++) {
+			subNGram.add(super.get(i));
+		}
+		return subNGram;
+	}
+
+	@Override
+	public String toString() {
+		if (super.size() == 0) {
+			return "";
+		}
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < super.size() - 1; i++) {
+			sb.append(super.get(i));
+			sb.append(" ");
+		}
+		sb.append(super.get(super.size() - 1));
+		return sb.toString();
+	}
+}

src/net/woodyfolsom/cs6601/p3/ngram/NGramDistribution.java

@@ -0,0 +1,6 @@
+package net.woodyfolsom.cs6601.p3.ngram;
+import java.util.HashMap;
+
+public class NGramDistribution extends HashMap<NGram, Integer> {
+	private static final long serialVersionUID = 1L;
+}

src/net/woodyfolsom/cs6601/p3/ngram/NGramModel.java

@@ -0,0 +1,361 @@
+package net.woodyfolsom.cs6601.p3.ngram;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import net.woodyfolsom.cs6601.p3.domain.Headline;
+
+public class NGramModel {
+	static final int MAX_N_GRAM_LENGTH = 3;
+	static final int RANDOM_LENGTH = 100;
+
+	private static final String START = "<start>";
+	private static final String END = "<end>";
+	private static final String UNK = "<unk>";
+
+	private Map<Integer, NGramDistribution> nGrams;
+	private int[] totalNGramCounts = new int[MAX_N_GRAM_LENGTH + 1];
+
+	private Pattern wordPattern = Pattern.compile("\\w+");
+	private Set<String> nonWords = new HashSet<String>();
+	private Set<String> words = new HashSet<String>();
+	private Set<String> wordsSeenOnce = new HashSet<String>();
+
+	double getProb(NGram nGram, NGram nMinusOneGram) {
+		NGramDistribution nGramDist = nGrams.get(nGram.size());
+		double prob;
+		if (nGramDist.containsKey(nGram)) {
+			// impossible for the bigram not to exist if the trigram does
+			NGramDistribution nMinusOneGramDist = nGrams.get(nGram.size() - 1);
+			int nMinusOneGramCount = nMinusOneGramDist.get(nMinusOneGram);
+			int nGramCount = nGramDist.get(nGram);
+			prob = (double) (nGramCount) / nMinusOneGramCount;
+		} else {
+			// Laplace smoothing
+			// prob = 1.0 / ((totalNGramCounts[nGram.size()] + 2.0));
+			NGram backoff = nGram.subNGram(1);
+			NGram backoffMinusOne = backoff.subNGram(0, backoff.size() - 1);
+			return getProb(backoff, backoffMinusOne);
+		}
+
+		return prob;
+	}
+
+	static String getRandomToken(Map<Integer, NGramDistribution> nGrams, int n,
+			NGram nMinusOneGram) {
+		List<Entry<NGram, Integer>> matchingNgrams = new ArrayList<Entry<NGram, Integer>>();
+		NGramDistribution ngDist = nGrams.get(n);
+
+		for (Entry<NGram, Integer> entry : ngDist.entrySet()) {
+			if (entry.getKey().startsWith(nMinusOneGram)) {
+				matchingNgrams.add(entry);
+			}
+		}
+
+		int totalCount = 0;
+		for (int i = 0; i < matchingNgrams.size(); i++) {
+			totalCount += matchingNgrams.get(i).getValue();
+		}
+		double random = Math.random();
+		int randomNGramIndex = (int) (random * totalCount);
+
+		totalCount = 0;
+		for (int i = 0; i < matchingNgrams.size(); i++) {
+			int currentCount = matchingNgrams.get(i).getValue();
+			if (randomNGramIndex < totalCount + currentCount) {
+				NGram ngram = matchingNgrams.get(i).getKey();
+				return ngram.get(ngram.size() - 1);
+			}
+			totalCount += currentCount;
+		}
+		return getRandomToken(nGrams, n - 1, nMinusOneGram.subNGram(1));
+	}
+
+	public NGramModel() {
+		// initialize Maps of 0-grams, unigrams, bigrams, trigrams...
+		nGrams = new HashMap<Integer, NGramDistribution>();
+		for (int i = 0; i <= MAX_N_GRAM_LENGTH; i++) {
+			nGrams.put(i, new NGramDistribution());
+		}
+	}
+
+	private void addNGram(int nGramLength, NGram nGram) {
+		if (nGram.size() < nGramLength) {
+			System.out.println("Cannot create " + nGramLength + "-gram from: "
+					+ nGram);
+		}
+
+		Map<NGram, Integer> nGramCounts = nGrams.get(nGramLength);
+		NGram nGramCopy = nGram.copy(nGramLength);
+
+		if (nGramCounts.containsKey(nGramCopy)) {
+			int nGramCount = nGramCounts.get(nGramCopy);
+			nGramCounts.put(nGramCopy, nGramCount + 1);
+		} else {
+			nGramCounts.put(nGramCopy, 1);
+		}
+	}
+
+	/**
+	 * Given an arbitrary String, replace punctutation with spaces, remove
+	 * non-alphanumeric characters, prepend with <START> token, append <END>
+	 * token.
+	 * 
+	 * @param rawHeadline
+	 * @return
+	 */
+	private String sanitize(String rawHeadline) {
+		String nonpunctuatedHeadline = rawHeadline.replaceAll(
+				"[\'\";:,\\]\\[]", " ");
+		String alphaNumericHeadline = nonpunctuatedHeadline.replaceAll(
+				"[^A-Za-z0-9 ]", "");
+		return START + " " + alphaNumericHeadline + " " + END;
+	}
+
+	private void calcPerplexity(List<Headline> validationSet, int nGramLimit,
+			boolean useUnk) throws FileNotFoundException, IOException {
+		List<String> fileByLines = new ArrayList<String>();
+		StringBuilder currentLine = new StringBuilder();
+
+		for (Headline headline : validationSet) {
+			String sanitizedLine = sanitize(headline.getText());
+			// split on whitespace
+			String[] tokens = sanitizedLine.toLowerCase().split("\\s+");
+			for (String token : tokens) {
+				if (!isWord(token)) {
+					continue;
+				}
+
+				String word;
+				if (!words.contains(token) && useUnk) {
+					word = UNK;
+					// words.add(token);
+				} else {
+					word = token;
+				}
+
+				if (END.equals(word)) {
+					currentLine.append(word);
+					fileByLines.add(currentLine.toString());
+					currentLine = new StringBuilder();
+				} else {
+					currentLine.append(word);
+					currentLine.append(" ");
+				}
+			}
+		}
+
+		int wordNum = 0;
+		int sentNum = 0;
+
+		double logProbT = 0.0;
+		for (String str : fileByLines) {
+			double logProbS = 0.0;
+			NGram currentNgram = new NGram(nGramLimit);
+			String[] tokens = str.split("\\s+");
+			for (String token : tokens) {
+				String word;
+				if (!words.contains(token) && useUnk) {
+					word = UNK;
+				} else {
+					word = token;
+				}
+				currentNgram.add(word);
+				NGram nMinusOneGram = currentNgram.subNGram(0,
+						currentNgram.size() - 1);
+
+				double prob = getProb(currentNgram, nMinusOneGram);
+
+				logProbS += Math.log(prob);
+			}
+			logProbT += logProbS;
+			wordNum += tokens.length;
+			sentNum++;
+		}
+
+		System.out.println("Evaluated " + sentNum + " sentences and " + wordNum
+				+ " words using " + nGramLimit + "-gram model.");
+		int N = wordNum + sentNum;
+		System.out.println("Total n-grams: " + N);
+		double perplexity = Math.pow(Math.E, (-1.0 / N) * logProbT);
+		System.out.println("Perplexity: over " + N
+				+ " recognized n-grams in verification corpus: " + perplexity);
+	}
+
+	private void generateModel(List<Headline> traininSet, boolean genRandom,
+			boolean useUnk) throws FileNotFoundException, IOException {
+		StringBuilder currentLine = new StringBuilder();
+		List<String> fileByLines = new ArrayList<String>();
+
+		for (Headline headline : traininSet) {
+			String headlineText = headline.getText();
+			if (headlineText.length() == 0) {
+				continue;
+			}
+			String sanitizedLine = sanitize(headline.getText());
+			// split on whitespace
+			String[] tokens = sanitizedLine.toLowerCase().split("\\s+");
+			for (String token : tokens) {
+				if (!isWord(token)) {
+					continue;
+				}
+
+				String word;
+				if (!wordsSeenOnce.contains(token) && useUnk) {
+					word = UNK;
+					wordsSeenOnce.add(token);
+				} else {
+					words.add(token);
+					word = token;
+				}
+
+				if (END.equals(word)) {
+					currentLine.append(word);
+					fileByLines.add(currentLine.toString());
+					currentLine = new StringBuilder();
+				} else {
+					currentLine.append(word);
+					currentLine.append(" ");
+				}
+			}
+		}
+
+		for (String str : fileByLines) {
+			System.out.println(str);
+			NGram currentNgram = new NGram(MAX_N_GRAM_LENGTH);
+			for (String token : str.split("\\s+")) {
+				currentNgram.add(token);
+				for (int i = 0; i <= currentNgram.size(); i++) {
+					addNGram(currentNgram.size() - i,
+							currentNgram.subNGram(i, currentNgram.size()));
+					totalNGramCounts[currentNgram.size() - i]++;
+				}
+			}
+		}
+
+		System.out.println("Most common words: ");
+		
+		List<Entry<NGram, Integer>> unigrams = new ArrayList<Entry<NGram, Integer>>(
+				nGrams.get(1).entrySet());
+		Collections.sort(unigrams, new NGramComparator());
+
+		List<Entry<NGram, Integer>> bigrams = new ArrayList<Entry<NGram, Integer>>(
+				nGrams.get(2).entrySet());
+		Collections.sort(bigrams, new NGramComparator());
+
+		List<Entry<NGram, Integer>> trigrams = new ArrayList<Entry<NGram, Integer>>(
+				nGrams.get(3).entrySet());
+		Collections.sort(trigrams, new NGramComparator());
+
+		for (int i = 1; i <= 10; i++) {
+			System.out
+					.println(i
+							+ ". "
+							+ unigrams.get(i - 1).getKey()
+							+ " : "
+							+ (((double) (unigrams.get(i - 1).getValue()) / totalNGramCounts[1])));
+		}
+
+		for (int i = 1; i <= 10; i++) {
+			System.out
+					.println(i
+							+ ". "
+							+ bigrams.get(i - 1).getKey()
+							+ " : "
+							+ (((double) (bigrams.get(i - 1).getValue()) / totalNGramCounts[2])));
+		}
+
+		for (int i = 1; i <= 10; i++) {
+			System.out
+					.println(i
+							+ ". "
+							+ trigrams.get(i - 1).getKey()
+							+ " : "
+							+ (((double) (trigrams.get(i - 1).getValue()) / totalNGramCounts[3])));
+		}
+		if (genRandom) {
+			for (int nGramLength = 1; nGramLength <= MAX_N_GRAM_LENGTH; nGramLength++) {
+				System.out.println("Random sentence of length " + RANDOM_LENGTH
+						+ " using " + nGramLength + "-gram language model:");
+				StringBuilder randomText = new StringBuilder();
+
+				NGram randomNminusOneGram = new NGram(nGramLength);
+				for (int i = 0; i < RANDOM_LENGTH; i++) {
+					String randomToken = getRandomToken(nGrams,
+							randomNminusOneGram.size() + 1, randomNminusOneGram);
+					NGram randomNGram = randomNminusOneGram.copy();
+					randomNGram.add(randomToken);
+					randomText.append(randomNGram.get(randomNGram.size() - 1));
+					randomText.append(" ");
+
+					if (randomNGram.size() < nGramLength) {
+						randomNminusOneGram = randomNGram;
+					} else {
+						randomNminusOneGram = randomNGram.subNGram(1);
+					}
+				}
+				System.out.println(randomText);
+				System.out.println();
+			}
+		}
+	}
+
+	private boolean isWord(String aString) {
+		if (aString == null || aString.length() == 0) {
+			return false;
+		}
+
+		if (nonWords.contains(aString)) {
+			return false;
+		}
+
+		if (START.equals(aString) || END.equals(aString) || UNK.equals(aString)) {
+			return true;
+		}
+
+		Matcher wordMatcher = wordPattern.matcher(aString);
+		if (wordMatcher.find()) {
+			return true;
+		}
+		nonWords.add(aString);
+		return false;
+	}
+
+	public void reportModel(List<Headline> trainingSet,
+			List<Headline> validationSet) {
+		try {
+			NGramModel ngm = new NGramModel();
+			boolean doCalcPerplexity = true;
+			ngm.generateModel(trainingSet, !doCalcPerplexity, doCalcPerplexity);
+			if (doCalcPerplexity) {
+				for (int i = 1; i <= MAX_N_GRAM_LENGTH; i++) {
+					ngm.calcPerplexity(validationSet, i, true);
+				}
+			}
+		} catch (FileNotFoundException fnfe) {
+			fnfe.printStackTrace(System.err);
+		} catch (IOException ioe) {
+			ioe.printStackTrace(System.err);
+		}
+	}
+
+	private class NGramComparator implements Comparator<Entry<NGram, Integer>> {
+
+		@Override
+		public int compare(Entry<NGram, Integer> o1, Entry<NGram, Integer> o2) {
+			return o2.getValue().compareTo(o1.getValue());
+		}
+
+	}
+}

src/net/woodyfolsom/cs6601/p3/svc/HeadlineService.java

@@ -9,4 +9,5 @@ public interface HeadlineService {
 	int insertHeadline(Headline headline);
 	int[] insertHeadlines(List<Headline> headline);
 	List<Headline> getHeadlines(String stock, Date date);
+	List<Headline> getHeadlines(String stock, Date startDate, Date endDate);
 }

src/net/woodyfolsom/cs6601/p3/svc/MySQLHeadlineServiceImpl.java

@@ -32,4 +32,9 @@ public class MySQLHeadlineServiceImpl implements HeadlineService {
 	public List<Headline> getHeadlines(String stock, Date date) {
 		return headlineDao.select(stock, date);
 	}
+	
+	@Override
+	public List<Headline> getHeadlines(String stock, Date startDate, Date endDate) {
+		return headlineDao.select(stock, startDate, endDate);
+	}
 }

src/net/woodyfolsom/cs6601/p3/svc/YahooHeadlineServiceImpl.java

@@ -86,4 +86,10 @@ public class YahooHeadlineServiceImpl implements HeadlineService {
 		String formattedDate = DATE_FORMATTER.format(date);
 		return QUERY_URL.replaceAll(STOCK_SYMBOL_FIELD, stock).replaceAll(STORY_DATE_FIELD, formattedDate);
 	}
+
+	@Override
+	public List<Headline> getHeadlines(String stock, Date startDate,
+			Date endDate) {
+		throw new UnsupportedOperationException("This implementation does not support getting headlines for a date range.");
+	}
 }