Fixed formatting issues.

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/kmeans/EuclideanDistance.java

@@ -9,8 +9,7 @@ public class EuclideanDistance implements Distance {
 
     @Override
     public double calculate(Map<String, Double> f1, Map<String, Double> f2) {
-		if (f1 == null || f2 == null)
+        if (f1 == null || f2 == null) throw new IllegalArgumentException("Feature vectors can't be null");
-			throw new IllegalArgumentException("Feature vectors can't be null");
 
         double sum = 0;
         for (String key : f1.keySet()) {

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/kmeans/KMeans.java

@@ -72,8 +72,11 @@ public class KMeans {
      * @return Collection of new and relocated centroids.
      */
     private static List<Centroid> relocateCentroids(Map<Centroid, List<Record>> clusters) {
-		return clusters.entrySet().stream()
+        return clusters
-		  .map(e -> average(e.getKey(), e.getValue())).collect(toList());
+          .entrySet()
+          .stream()
+          .map(e -> average(e.getKey(), e.getValue()))
+          .collect(toList());
     }
 
     /**
@@ -97,13 +100,18 @@ public class KMeans {
 
         // The average function works correctly if we clear all coordinates corresponding
         // to present record attributes
-		records.stream().flatMap(e -> e.getFeatures().keySet().stream())
+        records
+          .stream()
+          .flatMap(e -> e
+            .getFeatures()
+            .keySet()
+            .stream())
           .forEach(k -> average.put(k, 0.0));
 
         for (Record record : records) {
-			record.getFeatures().forEach(
+            record
-			  (k, v) -> average.compute(k, (k1, currentValue) -> v + currentValue)
+              .getFeatures()
-			);
+              .forEach((k, v) -> average.compute(k, (k1, currentValue) -> v + currentValue));
         }
 
         average.forEach((k, v) -> average.put(k, v / records.size()));
@@ -119,8 +127,7 @@ public class KMeans {
      * @param record   The feature vector.
      * @param centroid The centroid.
      */
-	private static void assignToCluster(Map<Centroid, List<Record>> clusters,
+    private static void assignToCluster(Map<Centroid, List<Record>> clusters, Record record, Centroid centroid) {
-	  Record record, Centroid centroid) {
         clusters.compute(centroid, (key, list) -> {
             if (list == null) {
                 list = new ArrayList<>();
@@ -140,8 +147,7 @@ public class KMeans {
      * @param distance  To calculate the distance between two items.
      * @return The nearest centroid to the given feature vector.
      */
-	private static Centroid nearestCentroid(Record record, List<Centroid> centroids,
+    private static Centroid nearestCentroid(Record record, List<Centroid> centroids, Distance distance) {
-	  Distance distance) {
         double minimumDistance = Double.MAX_VALUE;
         Centroid nearest = null;
 
@@ -174,7 +180,9 @@ public class KMeans {
         Map<String, Double> mins = new HashMap<>();
 
         for (Record record : records) {
-			record.getFeatures().forEach((key, value) -> {
+            record
+              .getFeatures()
+              .forEach((key, value) -> {
                   // compares the value with the current max and choose the bigger value between them
                   maxs.compute(key, (k1, max) -> max == null || value > max ? value : max);
 
@@ -183,8 +191,13 @@ public class KMeans {
               });
         }
 
-		Set<String> attributes = records.stream()
+        Set<String> attributes = records
-		  .flatMap(e -> e.getFeatures().keySet().stream()).collect(toSet());
+          .stream()
+          .flatMap(e -> e
+            .getFeatures()
+            .keySet()
+            .stream())
+          .collect(toSet());
         for (int i = 0; i < k; i++) {
             Map<String, Double> coordinates = new HashMap<>();
             for (String attribute : attributes) {
@@ -199,18 +212,13 @@ public class KMeans {
         return centroids;
     }
 
-	private static void applyPreconditions(List<Record> records, int k,
+    private static void applyPreconditions(List<Record> records, int k, Distance distance, int maxIterations) {
-	  Distance distance, int maxIterations) {
+        if (records == null || records.isEmpty()) throw new IllegalArgumentException("The dataset can't be empty");
-		if (records == null || records.isEmpty())
-			throw new IllegalArgumentException("The dataset can't be empty");
 
-		if (k <= 1)
+        if (k <= 1) throw new IllegalArgumentException("It doesn't make sense to have less than or equal to 1 cluster");
-			throw new IllegalArgumentException("It doesn't make sense to have less than or equal to 1 cluster");
 
-		if (distance == null)
+        if (distance == null) throw new IllegalArgumentException("The distance calculator is required");
-			throw new IllegalArgumentException("The distance calculator is required");
 
-		if (maxIterations <= 0)
+        if (maxIterations <= 0) throw new IllegalArgumentException("Max iterations should be a positive number");
-			throw new IllegalArgumentException("Max iterations should be a positive number");
     }
 }

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/kmeans/LastFm.java

@@ -23,7 +23,8 @@ public class LastFm {
       .addInterceptor(new LastFmService.Authenticator("put your API key here"))
       .build();
 
-	private static Retrofit retrofit = new Retrofit.Builder().client(okHttp)
+    private static Retrofit retrofit = new Retrofit.Builder()
+      .client(okHttp)
       .addConverterFactory(JacksonConverterFactory.create())
       .baseUrl("http://ws.audioscrobbler.com/")
       .build();
@@ -43,7 +44,10 @@ public class LastFm {
             System.out.println("------------------------------ CLUSTER -----------------------------------");
 
             System.out.println(sortedCentroid(key));
-			String members = String.join(", ", value.stream().map(Record::getDescription).collect(toSet()));
+            String members = String.join(", ", value
+              .stream()
+              .map(Record::getDescription)
+              .collect(toSet()));
             System.out.print(members);
 
             System.out.println();
@@ -67,7 +71,6 @@ public class LastFm {
             }
             child.put("children", nested);
 
-
             children.add(child);
         });
         json.put("children", children);
@@ -75,12 +78,21 @@ public class LastFm {
     }
 
     private static String dominantGenre(Centroid centroid) {
-		return centroid.getCoordinates().keySet().stream().limit(2).collect(Collectors.joining(", "));
+        return centroid
+          .getCoordinates()
+          .keySet()
+          .stream()
+          .limit(2)
+          .collect(Collectors.joining(", "));
     }
 
     private static Centroid sortedCentroid(Centroid key) {
-		List<Map.Entry<String, Double>> entries = new ArrayList<>(key.getCoordinates().entrySet());
+        List<Map.Entry<String, Double>> entries = new ArrayList<>(key
-		entries.sort((e1, e2) -> e2.getValue().compareTo(e1.getValue()));
+          .getCoordinates()
+          .entrySet());
+        entries.sort((e1, e2) -> e2
+          .getValue()
+          .compareTo(e1.getValue()));
 
         Map<String, Double> sorted = new LinkedHashMap<>();
         for (Map.Entry<String, Double> entry : entries) {
@@ -90,14 +102,19 @@ public class LastFm {
         return new Centroid(sorted);
     }
 
-	private static List<Record> datasetWithTaggedArtists(List<String> artists,
+    private static List<Record> datasetWithTaggedArtists(List<String> artists, Set<String> topTags) throws IOException {
-	  Set<String> topTags) throws IOException {
         List<Record> records = new ArrayList<>();
         for (String artist : artists) {
-			Map<String, Double> tags = lastFm.topTagsFor(artist).execute().body().all();
+            Map<String, Double> tags = lastFm
+              .topTagsFor(artist)
+              .execute()
+              .body()
+              .all();
 
             // Only keep popular tags.
-			tags.entrySet().removeIf(e -> !topTags.contains(e.getKey()));
+            tags
+              .entrySet()
+              .removeIf(e -> !topTags.contains(e.getKey()));
 
             records.add(new Record(artist, tags));
         }
@@ -105,13 +122,21 @@ public class LastFm {
     }
 
     private static Set<String> getTop100Tags() throws IOException {
-		return lastFm.topTags().execute().body().all();
+        return lastFm
+          .topTags()
+          .execute()
+          .body()
+          .all();
     }
 
     private static List<String> getTop100Artists() throws IOException {
         List<String> artists = new ArrayList<>();
         for (int i = 1; i <= 2; i++) {
-			artists.addAll(lastFm.topArtists(i).execute().body().all());
+            artists.addAll(lastFm
+              .topArtists(i)
+              .execute()
+              .body()
+              .all());
         }
 
         return artists;

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/kmeans/LastFmService.java

@@ -45,8 +45,17 @@ public interface LastFmService {
 
         @Override
         public Response intercept(Chain chain) throws IOException {
-			HttpUrl url = chain.request().url().newBuilder().addQueryParameter("api_key", apiKey).build();
+            HttpUrl url = chain
-			Request request = chain.request().newBuilder().url(url).build();
+              .request()
+              .url()
+              .newBuilder()
+              .addQueryParameter("api_key", apiKey)
+              .build();
+            Request request = chain
+              .request()
+              .newBuilder()
+              .url(url)
+              .build();
 
             return chain.proceed(request);
         }
@@ -60,15 +69,17 @@ public interface LastFmService {
         @SuppressWarnings("unchecked")
         public Set<String> all() {
             List<Map<String, Object>> topTags = (List<Map<String, Object>>) tags.get("tag");
-			return topTags.stream().map(e -> ((String) e.get("name"))).collect(Collectors.toSet());
+            return topTags
+              .stream()
+              .map(e -> ((String) e.get("name")))
+              .collect(Collectors.toSet());
         }
     }
 
     @JsonAutoDetect(fieldVisibility = ANY)
     class Tags {
 
-		@JsonProperty("toptags")
+        @JsonProperty("toptags") private Map<String, Object> topTags;
-		private Map<String, Object> topTags;
 
         @SuppressWarnings("unchecked")
         public Map<String, Double> all() {
@@ -80,8 +91,7 @@ public interface LastFmService {
                 }
 
                 return all;
-			}
+            } catch (Exception e) {
-			catch (Exception e) {
                 return Collections.emptyMap();
             }
         }
@@ -96,9 +106,11 @@ public interface LastFmService {
         public List<String> all() {
             try {
                 List<Map<String, Object>> artists = (List<Map<String, Object>>) this.artists.get("artist");
-				return artists.stream().map(e -> ((String) e.get("name"))).collect(toList());
+                return artists
-			}
+                  .stream()
-			catch (Exception e) {
+                  .map(e -> ((String) e.get("name")))
+                  .collect(toList());
+            } catch (Exception e) {
                 return Collections.emptyList();
             }
         }

algorithms-miscellaneous-3/src/main/java/com/baeldung/algorithms/kmeans/Record.java

@@ -39,7 +39,9 @@ public class Record {
 
     @Override
     public String toString() {
-		String prefix = description == null || description.trim().isEmpty() ? "Record" : description;
+        String prefix = description == null || description
+          .trim()
+          .isEmpty() ? "Record" : description;
 
         return prefix + ": " + features;
     }
@@ -49,8 +51,7 @@ public class Record {
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
         Record record = (Record) o;
-		return Objects.equals(getDescription(), record.getDescription()) &&
+        return Objects.equals(getDescription(), record.getDescription()) && Objects.equals(getFeatures(), record.getFeatures());
-		  Objects.equals(getFeatures(), record.getFeatures());
     }
 
     @Override

algorithms-miscellaneous-3/src/main/resources/kmeans/radial.html

@@ -6,9 +6,11 @@
         stroke: steelblue;
         stroke-width: 1.5px;
     }
+
     .node {
         font: 10px sans-serif;
     }
+
     .link {
         fill: none;
         stroke: #ccc;
@@ -21,15 +23,19 @@
     var diameter = 1100;
     var tree = d3.layout.tree()
         .size([360, diameter / 2 - 300])
-        .separation(function(a, b) { return (a.parent == b.parent ? 1 : 2) / a.depth; });
+        .separation(function (a, b) {
+            return (a.parent == b.parent ? 1 : 2) / a.depth;
+        });
     var diagonal = d3.svg.diagonal.radial()
-        .projection(function(d) { return [d.y, d.x / 180 * Math.PI]; });
+        .projection(function (d) {
+            return [d.y, d.x / 180 * Math.PI];
+        });
     var svg = d3.select("body").append("svg")
         .attr("width", diameter)
         .attr("height", diameter - 150)
         .append("g")
         .attr("transform", "translate(" + diameter / 2 + "," + diameter / 2 + ")");
-    d3.json("lastfm.json", function(error, root) {
+    d3.json("lastfm.json", function (error, root) {
         var nodes = tree.nodes(root),
             links = tree.links(nodes);
         var link = svg.selectAll(".link")
@@ -41,14 +47,22 @@
             .data(nodes)
             .enter().append("g")
             .attr("class", "node")
-            .attr("transform", function(d) { return "rotate(" + (d.x - 90) + ")translate(" + d.y + ")"; })
+            .attr("transform", function (d) {
+                return "rotate(" + (d.x - 90) + ")translate(" + d.y + ")";
+            })
         node.append("circle")
             .attr("r", 4.5);
         node.append("text")
             .attr("dy", ".31em")
-            .attr("text-anchor", function(d) { return d.x < 180 ? "start" : "end"; })
+            .attr("text-anchor", function (d) {
-            .attr("transform", function(d) { return d.x < 180 ? "translate(8)" : "rotate(180)translate(-8)"; })
+                return d.x < 180 ? "start" : "end";
-            .text(function(d) { return d.name; });
+            })
+            .attr("transform", function (d) {
+                return d.x < 180 ? "translate(8)" : "rotate(180)translate(-8)";
+            })
+            .text(function (d) {
+                return d.name;
+            });
     });
     d3.select(self.frameElement).style("height", diameter - 150 + "px");
 </script>