diff --git a/core-java/src/main/java/com/baeldung/algorithms/slope_one/SlopeOne.java b/core-java/src/main/java/com/baeldung/algorithms/slope_one/SlopeOne.java
index 800a86884f..f11538356a 100644
--- a/core-java/src/main/java/com/baeldung/algorithms/slope_one/SlopeOne.java
+++ b/core-java/src/main/java/com/baeldung/algorithms/slope_one/SlopeOne.java
@@ -11,8 +11,8 @@ import java.util.Map.Entry;
  */
 public class SlopeOne {
 
-	private static Map<Item, Map<Item, Double>> differencesMatrix = new HashMap<>();
-	private static Map<Item, Map<Item, Integer>> frequenciesMatrix = new HashMap<>();
+	private static Map<Item, Map<Item, Double>> diff = new HashMap<>();
+	private static Map<Item, Map<Item, Integer>> freq = new HashMap<>();
 	private static Map<User, HashMap<Item, Double>> inputData;
 	private static Map<User, HashMap<Item, Double>> outputData = new HashMap<>();
 
@@ -28,33 +28,36 @@ public class SlopeOne {
 	 * Based on the available data, calculate the relationships between the
 	 * items and number of occurences
 	 * 
-	 * @param data existing user data and their items' ratings
+	 * @param data
+	 *            existing user data and their items' ratings
 	 */
 	private static void buildDifferencesMatrix(Map<User, HashMap<Item, Double>> data) {
 		for (HashMap<Item, Double> user : data.values()) {
-			for (Entry<Item, Double> entry : user.entrySet()) {
-				if (!differencesMatrix.containsKey(entry.getKey())) {
-					differencesMatrix.put(entry.getKey(), new HashMap<Item, Double>());
-					frequenciesMatrix.put(entry.getKey(), new HashMap<Item, Integer>());
+			for (Entry<Item, Double> e : user.entrySet()) {
+				if (!diff.containsKey(e.getKey())) {
+					diff.put(e.getKey(), new HashMap<Item, Double>());
+					freq.put(e.getKey(), new HashMap<Item, Integer>());
 				}
-				for (Entry<Item, Double> entry2 : user.entrySet()) {
+				for (Entry<Item, Double> e2 : user.entrySet()) {
 					int oldCount = 0;
-					if (frequenciesMatrix.get(entry.getKey()).containsKey(entry2.getKey()))
-						oldCount = frequenciesMatrix.get(entry.getKey()).get(entry2.getKey()).intValue();
+					if (freq.get(e.getKey()).containsKey(e2.getKey())) {
+						oldCount = freq.get(e.getKey()).get(e2.getKey()).intValue();
+					}
 					double oldDiff = 0.0;
-					if (differencesMatrix.get(entry.getKey()).containsKey(entry2.getKey()))
-						oldDiff = differencesMatrix.get(entry.getKey()).get(entry2.getKey()).doubleValue();
-					double observedDiff = entry.getValue() - entry2.getValue();
-					frequenciesMatrix.get(entry.getKey()).put(entry2.getKey(), oldCount + 1);
-					differencesMatrix.get(entry.getKey()).put(entry2.getKey(), oldDiff + observedDiff);
+					if (diff.get(e.getKey()).containsKey(e2.getKey())) {
+						oldDiff = diff.get(e.getKey()).get(e2.getKey()).doubleValue();
+					}
+					double observedDiff = e.getValue() - e2.getValue();
+					freq.get(e.getKey()).put(e2.getKey(), oldCount + 1);
+					diff.get(e.getKey()).put(e2.getKey(), oldDiff + observedDiff);
 				}
 			}
 		}
-		for (Item j : differencesMatrix.keySet()) {
-			for (Item i : differencesMatrix.get(j).keySet()) {
-				double oldvalue = differencesMatrix.get(j).get(i).doubleValue();
-				int count = frequenciesMatrix.get(j).get(i).intValue();
-				differencesMatrix.get(j).put(i, oldvalue / count);
+		for (Item j : diff.keySet()) {
+			for (Item i : diff.get(j).keySet()) {
+				double oldValue = diff.get(j).get(i).doubleValue();
+				int count = freq.get(j).get(i).intValue();
+				diff.get(j).put(i, oldValue / count);
 			}
 		}
 		printData(data);
@@ -64,41 +67,42 @@ public class SlopeOne {
 	 * Based on existing data predict all missing ratings. If prediction is not
 	 * possible, the value will be equal to -1
 	 * 
-	 * @param data existing user data and their items' ratings
+	 * @param data
+	 *            existing user data and their items' ratings
 	 */
 	private static void predict(Map<User, HashMap<Item, Double>> data) {
-		HashMap<Item, Double> predictions = new HashMap<Item, Double>();
-		HashMap<Item, Integer> frequencies = new HashMap<Item, Integer>();
-		for (Item j : differencesMatrix.keySet()) {
-			frequencies.put(j, 0);
-			predictions.put(j, 0.0);
+		HashMap<Item, Double> uPred = new HashMap<Item, Double>();
+		HashMap<Item, Integer> uFreq = new HashMap<Item, Integer>();
+		for (Item j : diff.keySet()) {
+			uFreq.put(j, 0);
+			uPred.put(j, 0.0);
 		}
-		for (Entry<User, HashMap<Item, Double>> entry : data.entrySet()) {
-			for (Item j : entry.getValue().keySet()) {
-				for (Item k : differencesMatrix.keySet()) {
+		for (Entry<User, HashMap<Item, Double>> e : data.entrySet()) {
+			for (Item j : e.getValue().keySet()) {
+				for (Item k : diff.keySet()) {
 					try {
-						double newValue = (differencesMatrix.get(k).get(j).doubleValue()
-								+ entry.getValue().get(j).doubleValue()) * frequenciesMatrix.get(k).get(j).intValue();
-						predictions.put(k, predictions.get(k) + newValue);
-						frequencies.put(k, frequencies.get(k) + frequenciesMatrix.get(k).get(j).intValue());
-					} catch (NullPointerException e) {
+						double predictedValue = diff.get(k).get(j).doubleValue() + e.getValue().get(j).doubleValue();
+						double finalValue = predictedValue * freq.get(k).get(j).intValue();
+						uPred.put(k, uPred.get(k) + finalValue);
+						uFreq.put(k, uFreq.get(k) + freq.get(k).get(j).intValue());
+					} catch (NullPointerException e1) {
 					}
 				}
 			}
-			HashMap<Item, Double> cleanPredictions = new HashMap<Item, Double>();
-			for (Item j : predictions.keySet()) {
-				if (frequencies.get(j) > 0) {
-					cleanPredictions.put(j, predictions.get(j).doubleValue() / frequencies.get(j).intValue());
+			HashMap<Item, Double> clean = new HashMap<Item, Double>();
+			for (Item j : uPred.keySet()) {
+				if (uFreq.get(j) > 0) {
+					clean.put(j, uPred.get(j).doubleValue() / uFreq.get(j).intValue());
 				}
 			}
 			for (Item j : InputData.items) {
-				if (entry.getValue().containsKey(j)) {
-					cleanPredictions.put(j, entry.getValue().get(j));
+				if (e.getValue().containsKey(j)) {
+					clean.put(j, e.getValue().get(j));
 				} else {
-					cleanPredictions.put(j, -1.0);
+					clean.put(j, -1.0);
 				}
 			}
-			outputData.put(entry.getKey(), cleanPredictions);
+			outputData.put(e.getKey(), clean);
 		}
 		printData(outputData);
 	}