Fixed the single line if statements.

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

@@ -23,8 +23,12 @@ public class Centroid {
 
     @Override
     public boolean equals(Object o) {
-        if (this == o) return true;
+        if (this == o) {
-        if (o == null || getClass() != o.getClass()) return false;
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
         Centroid centroid = (Centroid) o;
         return Objects.equals(getCoordinates(), centroid.getCoordinates());
     }

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

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

@@ -55,7 +55,9 @@ public class KMeans {
             // if the assignment does not change, then the algorithm terminates
             boolean shouldTerminate = isLastIteration || clusters.equals(lastState);
             lastState = clusters;
-            if (shouldTerminate) break;
+            if (shouldTerminate) {
+                break;
+            }
 
             // at the end of each iteration we should relocate the centroids
             centroids = relocateCentroids(clusters);
@@ -92,7 +94,9 @@ public class KMeans {
      */
     private static Centroid average(Centroid centroid, List<Record> records) {
         // if this cluster is empty, then we shouldn't move the centroid
-        if (records == null || records.isEmpty()) return centroid;
+        if (records == null || records.isEmpty()) {
+            return centroid;
+        }
 
         // Since some records don't have all possible attributes, we initialize
         // average coordinates equal to current centroid coordinates
@@ -213,12 +217,20 @@ public class KMeans {
     }
 
     private static void applyPreconditions(List<Record> records, int k, 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) throw new IllegalArgumentException("It doesn't make sense to have less than or equal to 1 cluster");
+        if (k <= 1) {
+            throw new IllegalArgumentException("It doesn't make sense to have less than or equal to 1 cluster");
+        }
 
-        if (distance == null) throw new IllegalArgumentException("The distance calculator is required");
+        if (distance == null) {
+            throw new IllegalArgumentException("The distance calculator is required");
+        }
 
-        if (maxIterations <= 0) throw new IllegalArgumentException("Max iterations should be a positive number");
+        if (maxIterations <= 0) {
+            throw new IllegalArgumentException("Max iterations should be a positive number");
+        }
     }
 }

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

@@ -48,8 +48,12 @@ public class Record {
 
     @Override
     public boolean equals(Object o) {
-        if (this == o) return true;
+        if (this == o) {
-        if (o == null || getClass() != o.getClass()) return false;
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
         Record record = (Record) o;
         return Objects.equals(getDescription(), record.getDescription()) && Objects.equals(getFeatures(), record.getFeatures());
     }