Add generic Node classes (#2782)

Co-authored-by: Andrii Siriak <siryaka@gmail.com>

DevUtils/Nodes/Node.java

@@ -0,0 +1,36 @@
+package DevUtils.Nodes;
+
+/**
+ * Base class for any node implementation which
+ * contains a generic type variable.
+ * 
+ * All known subclasses: {@link TreeNode}, {@link SimpleNode}.
+ * 
+ * @param <E> The type of the data held in the Node.
+ * 
+ * @author <a href="https://github.com/aitorfi">aitorfi</a>
+ */
+public abstract class Node<E> {
+    /** Generic type data stored in the Node. */
+    private E data;
+
+    /** Empty constructor. */
+    public Node() {}
+
+    /**
+     * Initializes the Nodes' data.
+     * 
+     * @param data Value to which data will be initialized.
+     */
+    public Node(E data) {
+        this.data = data;
+    }
+
+    public E getData() {
+        return data;
+    }
+
+    public void setData(E data) {
+        this.data = data;
+    }
+}