YL-2 Add: Implementation to Node & Nodes classes

2-0-data-structures-and-algorithms/2-2-1-node/src/main/java/com/bobobode/cs/Node.java

@@ -9,5 +9,27 @@
  * @author Taras Boychuk
  */
 public class Node<T> {
-    // todo:
+    T element;
+    Node<T> reference;
+
+    public Node(T element) {
+        this.element =
+                element;
+    }
+
+    public T getElement() {
+        return element;
+    }
+
+    public void setElement(T element) {
+        this.element = element;
+    }
+
+    public Node<T> getReference() {
+        return reference;
+    }
+
+    public void setReference(Node<T> reference) {
+        this.reference = reference;
+    }
 }

2-0-data-structures-and-algorithms/2-2-1-node/src/main/java/com/bobobode/cs/Nodes.java

@@ -2,6 +2,9 @@
 
 import com.bobocode.util.ExerciseNotCompletedException;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * A class that consists of static methods only and provides util methods for {@link Node}.
  * <p><p>
@@ -22,7 +25,7 @@ private Nodes() {
      * @return a new instance of {@link Node}
      */
     public static <T> Node<T> create(T element) {
-        throw new ExerciseNotCompletedException(); // todo:
+       return new Node<>(element);
     }
 
     /**
@@ -33,7 +36,7 @@ public static <T> Node<T> create(T element) {
      * @param <T>    a genetic type
      */
     public static <T> void link(Node<T> first, Node<T> second) {
-        throw new ExerciseNotCompletedException(); // todo:
+        first.reference = second;
     }
 
     /**
@@ -46,7 +49,10 @@ public static <T> void link(Node<T> first, Node<T> second) {
      * @return a reference to a first node created based on firstElement
      */
     public static <T> Node<T> pairOf(T firstElement, T secondElement) {
-        throw new ExerciseNotCompletedException(); // todo:
+        Node<T> firstNode = new Node<>(firstElement);
+        firstNode.reference = new Node<>(secondElement);
+
+        return firstNode;
     }
 
     /**
@@ -60,7 +66,13 @@ public static <T> Node<T> pairOf(T firstElement, T secondElement) {
      * @return a reference to the first node
      */
     public static <T> Node<T> closedPairOf(T firstElement, T secondElement) {
-        throw new ExerciseNotCompletedException(); // todo:
+        Node<T> firstNode = new Node<>(firstElement);
+        Node<T> secondNode = new Node<>(secondElement);
+
+        firstNode.reference = secondNode;
+        secondNode.reference = firstNode;
+
+        return firstNode;
     }
 
     /**
@@ -72,7 +84,13 @@ public static <T> Node<T> closedPairOf(T firstElement, T secondElement) {
      * @return a reference to the first element of the chain
      */
     public static <T> Node<T> chainOf(T... elements) {
-        throw new ExerciseNotCompletedException(); // todo:
+        Node<T> firstNode = new Node<>(elements[0]);
+        Node<T> current = firstNode;
+        for (int i = 1; i < elements.length; i++) {
+            current.reference = new Node<>(elements[i]);
+            current = current.reference;
+        }
+        return firstNode;
     }
 
     /**
@@ -85,6 +103,16 @@ public static <T> Node<T> chainOf(T... elements) {
      * @return a reference to the first element of the chain
      */
     public static <T> Node<T> circleOf(T... elements) {
-        throw new ExerciseNotCompletedException(); // todo:
+        Node<T> firstNode = new Node<>(elements[0]);
+        Node<T> current = firstNode;
+        for (int i = 1; i < elements.length; i++) {
+            current.reference = new Node<>(elements[i]);
+            current = current.reference;
+
+            if(i == elements.length -1){
+                current.reference = firstNode;
+            }
+        }
+        return firstNode;
     }
 }