guava library updated to 27.0.1

upgraded guava library to 27.0.1
added javadoc

algorithms-miscellaneous-1/pom.xml

@@ -82,7 +82,7 @@
         <commons-math3.version>3.6.1</commons-math3.version>
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
-        <guava.version>25.1-jre</guava.version>
+        <guava.version>27.0.1-jre</guava.version>
     </properties>
 
 </project>

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/ApacheCommonsCombinationGenerator.java

@@ -7,11 +7,23 @@
 
 public class ApacheCommonsCombinationGenerator {
 
-    public static void main(String[] args) {
-        Iterator<int[]> iterator = CombinatoricsUtils.combinationsIterator(5, 3);
+    private static final int N = 6;
+    private static final int R = 3;
+
+    /** 
+     * Print all combinations of r elements from a set
+     * @param n - number of elements in set
+     * @param r - number of elements in selection
+     */
+    public static void generate(int n, int r) {
+        Iterator<int[]> iterator = CombinatoricsUtils.combinationsIterator(n, r);
         while (iterator.hasNext()) {
             final int[] combination = iterator.next();
             System.out.println(Arrays.toString(combination));
         }
     }
+
+    public static void main(String[] args) {
+        generate(N, R);
+    }
 }

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/IterativeCombinationGenerator.java

@@ -5,21 +5,29 @@
 import java.util.List;
 
 public class IterativeCombinationGenerator {
-    
+
     private static final int N = 5;
     private static final int R = 2;
 
+    /**
+     * Generate all combinations of r elements from a set
+     * @param n the number of elements in input set
+     * @param r the number of elements in a combination
+     * @return the list containing all combinations
+     */
     public List<int[]> generate(int n, int r) {
         List<int[]> combinations = new ArrayList<>();
         int[] combination = new int[r];
 
+        // initialize with lowest lexicographic combination
         for (int i = 0; i < r; i++) {
             combination[i] = i;
         }
 
         while (combination[r - 1] < n) {
             combinations.add(combination.clone());
 
+            // generate next combination in lexicographic order
             int t = r - 1;
             while (t != 0 && combination[t] == n - r + t) {
                 t--;
@@ -41,5 +49,4 @@ public static void main(String[] args) {
             System.out.println(Arrays.toString(combination));
         }
     }
-
 }

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/SelectionRecursiveCombinationGenerator.java

@@ -9,12 +9,26 @@ public class SelectionRecursiveCombinationGenerator {
     private static final int N = 6;
     private static final int R = 3;
 
+    /** 
+     * Generate all combinations of r elements from a set
+     * @param n - number of elements in input set
+     * @param r - number of elements to be chosen
+     * @return the list containing all combinations
+     */
     public List<int[]> generate(int n, int r) {
         List<int[]> combinations = new ArrayList<>();
         helper(combinations, new int[r], 0, n - 1, 0);
         return combinations;
     }
 
+    /** 
+     * Choose elements from set by recursing over elements selected
+     * @param combinations - List to store generated combinations
+     * @param data - current combination
+     * @param start - starting element of remaining set
+     * @param end - last element of remaining set
+     * @param index - number of elements chosen so far.
+     */
     private void helper(List<int[]> combinations, int data[], int start, int end, int index) {
         if (index == data.length) {
             int[] combination = data.clone();
@@ -31,9 +45,9 @@ private void helper(List<int[]> combinations, int data[], int start, int end, in
     public static void main(String[] args) {
         SelectionRecursiveCombinationGenerator generator = new SelectionRecursiveCombinationGenerator();
         List<int[]> combinations = generator.generate(N, R);
-        System.out.println(combinations.size());
         for (int[] combination : combinations) {
             System.out.println(Arrays.toString(combination));
         }
+        System.out.printf("generated %d combinations of %d items from %d ", combinations.size(), R, N);
     }
 }

algorithms-miscellaneous-1/src/main/java/com/baeldung/algorithms/combination/SetRecursiveCombinationGenerator.java

@@ -6,33 +6,45 @@
 
 public class SetRecursiveCombinationGenerator {
 
-    private static final int N = 6;
-    private static final int R = 3;
+    private static final int N = 5;
+    private static final int R = 2;
 
+    /** 
+     * Generate all combinations of r elements from a set
+     * @param n - number of elements in set
+     * @param r - number of elements in selection
+     * @return the list containing all combinations
+     */
     public List<int[]> generate(int n, int r) {
         List<int[]> combinations = new ArrayList<>();
-        helper(combinations, new int[r], 0, n - 1, 0, r);
+        helper(combinations, new int[r], 0, n-1, 0);
         return combinations;
     }
 
-    private void helper(List<int[]> combinations, int data[], int start, int end, int index, int r) {
+    /**
+     * @param combinations - List to contain the generated combinations
+     * @param data - List of elements in the selection
+     * @param start - index of the starting element in the remaining set
+     * @param end - index of the last element in the set  
+     * @param index - number of elements selected so far
+     */
+    private void helper(List<int[]> combinations, int data[], int start, int end, int index) {
         if (index == data.length) {
             int[] combination = data.clone();
             combinations.add(combination);
-
         } else if (start <= end) {
             data[index] = start;
-            helper(combinations, data, start + 1, end, index + 1, r);
-            helper(combinations, data, start + 1, end, index, r);
+            helper(combinations, data, start + 1, end, index + 1);
+            helper(combinations, data, start + 1, end, index);
         }
     }
 
     public static void main(String[] args) {
         SetRecursiveCombinationGenerator generator = new SetRecursiveCombinationGenerator();
         List<int[]> combinations = generator.generate(N, R);
-        System.out.println(combinations.size());
         for (int[] combination : combinations) {
             System.out.println(Arrays.toString(combination));
         }
+        System.out.printf("generated %d combinations of %d items from %d ", combinations.size(), R, N);
     }
 }