Add generic Node classes (#2782)

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

DevUtils/Nodes/TreeNode.java

@@ -0,0 +1,72 @@
+package DevUtils.Nodes;
+
+/**
+ * Base class for any tree node which
+ * holds a reference to the parent node.
+ * 
+ * All known subclasses: {@link SimpleTreeNode}, {@link LargeTreeNode}.
+ * 
+ * @param <E> The type of the data held in the Node.
+ * 
+ * @author <a href="https://github.com/aitorfi">aitorfi</a>
+ */
+public abstract class TreeNode<E> extends Node<E> {
+    /** Refernce to the parent Node. */
+    private TreeNode<E> parentNode;
+    /** Indicates the depth at which this node is in the tree. */
+    private int depth;
+
+    /** Empty contructor. */
+    public TreeNode() {
+        super();
+        depth = 0;
+    }
+
+    /**
+     * Initializes the Nodes' data.
+     * 
+     * @param data Value to which data will be initialized.
+     * @see Node#Node(Object)
+     */
+    public TreeNode(E data) {
+        super(data);
+        depth = 0;
+    }
+
+    /**
+     * Initializes the Nodes' data and parent node reference.
+     * 
+     * @param data Value to which data will be initialized.
+     * @param parentNode Value to which the nodes' parent reference will be set.
+     */
+    public TreeNode(E data, TreeNode<E> parentNode) {
+        super(data);
+        this.parentNode = parentNode;
+        depth = this.parentNode.getDepth() + 1;
+    }
+
+    /**
+     * @return True if the node is a leaf node, otherwise false.
+     */
+    public abstract boolean isLeafNode();
+
+    /**
+     * @return True if the node is the root node, otherwise false.
+     */
+    public boolean isRootNode() {
+        return (parentNode == null);
+    }
+
+    public TreeNode<E> getParent() {
+        return parentNode;
+    }
+
+    public void setParent(TreeNode<E> parentNode) {
+        this.parentNode = parentNode;
+        depth = this.parentNode.getDepth() + 1;
+    }
+
+    public int getDepth() {
+        return depth;
+    }
+}