Java Data Structures Binary Tree

import java.util.Stack;

class Node {
   public int iData; 
   public double dData; 
   public Node leftChild; 
   public Node rightChild; 

   public void displayNode() 
   {/*from   w w  w .  ja  va  2s.  c  o  m*/
      System.out.print('{');
      System.out.print(iData);
      System.out.print(", ");
      System.out.print(dData);
      System.out.print("} ");
   }
} 

class Tree {
   private Node root; // first node of tree

   public Tree() {
      root = null;
   }

   public Node find(int key) {
      Node current = root;
      while (current.iData != key) {
         if (key < current.iData)
            current = current.leftChild;
         else
            current = current.rightChild;
         if (current == null)
            return null;
      }
      return current;
   }

   public void insert(int id, double dd) {
      Node newNode = new Node();
      newNode.iData = id;
      newNode.dData = dd;
      if (root == null)
         root = newNode;
      else {
         Node current = root;
         Node parent;
         while (true) {
            parent = current;
            if (id < current.iData) {
               current = current.leftChild;
               if (current == null) {
                  parent.leftChild = newNode;
                  return;
               }
            } else {
               current = current.rightChild;
               if (current == null) {
                  parent.rightChild = newNode;
                  return;
               }
            }
         }
      }
   }

   public boolean delete(int key) {
      Node current = root;
      Node parent = root;
      boolean isLeftChild = true;

      while (current.iData != key) {
         parent = current;
         if (key < current.iData) {
            isLeftChild = true;
            current = current.leftChild;
         } else {
            isLeftChild = false;
            current = current.rightChild;
         }
         if (current == null)
            return false;
      }

      if (current.leftChild == null && current.rightChild == null) {
         if (current == root)
            root = null;
         else if (isLeftChild)
            parent.leftChild = null;
         else
            parent.rightChild = null;
      }

      else if (current.rightChild == null)
         if (current == root)
            root = current.leftChild;
         else if (isLeftChild)
            parent.leftChild = current.leftChild;
         else
            parent.rightChild = current.leftChild;

      else if (current.leftChild == null)
         if (current == root)
            root = current.rightChild;
         else if (isLeftChild)
            parent.leftChild = current.rightChild;
         else
            parent.rightChild = current.rightChild;

      else {
         Node successor = getSuccessor(current);

         if (current == root)
            root = successor;
         else if (isLeftChild)
            parent.leftChild = successor;
         else
            parent.rightChild = successor;

         successor.leftChild = current.leftChild;
      }
      return true;
   }

   private Node getSuccessor(Node delNode) {
      Node successorParent = delNode;
      Node successor = delNode;
      Node current = delNode.rightChild;
      while (current != null) {
         successorParent = successor;
         successor = current;
         current = current.leftChild;
      }
      if (successor != delNode.rightChild) {
         successorParent.leftChild = successor.rightChild;
         successor.rightChild = delNode.rightChild;
      }
      return successor;
   }

   public void traverse(int traverseType) {
      switch (traverseType) {
      case 1:
         System.out.print("\nPreorder traversal: ");
         preOrder(root);
         break;
      case 2:
         System.out.print("\nInorder traversal:  ");
         inOrder(root);
         break;
      case 3:
         System.out.print("\nPostorder traversal: ");
         postOrder(root);
         break;
      }
      System.out.println();
   }

   private void preOrder(Node localRoot) {
      if (localRoot != null) {
         System.out.print(localRoot.iData + " ");
         preOrder(localRoot.leftChild);
         preOrder(localRoot.rightChild);
      }
   }

   private void inOrder(Node localRoot) {
      if (localRoot != null) {
         inOrder(localRoot.leftChild);
         System.out.print(localRoot.iData + " ");
         inOrder(localRoot.rightChild);
      }
   }

   private void postOrder(Node localRoot) {
      if (localRoot != null) {
         postOrder(localRoot.leftChild);
         postOrder(localRoot.rightChild);
         System.out.print(localRoot.iData + " ");
      }
   }

   public void displayTree() {
      Stack<Node> globalStack = new Stack<>();
      globalStack.push(root);
      int nBlanks = 32;
      boolean isRowEmpty = false;
      System.out.println("......................................................");
      while (isRowEmpty == false) {
         Stack<Node> localStack = new Stack<>();
         isRowEmpty = true;

         for (int j = 0; j < nBlanks; j++)
            System.out.print(' ');

         while (globalStack.isEmpty() == false) {
            Node temp = (Node) globalStack.pop();
            if (temp != null) {
               System.out.print(temp.iData);
               localStack.push(temp.leftChild);
               localStack.push(temp.rightChild);

               if (temp.leftChild != null || temp.rightChild != null)
                  isRowEmpty = false;
            } else {
               System.out.print("--");
               localStack.push(null);
               localStack.push(null);
            }
            for (int j = 0; j < nBlanks * 2 - 2; j++)
               System.out.print(' ');
         }
         System.out.println();
         nBlanks /= 2;
         while (localStack.isEmpty() == false)
            globalStack.push(localStack.pop());
      }
      System.out.println("......................................................");
   }

}

public class Main {
   public static void main(String[] args) {
      int value;
      Tree theTree = new Tree();

      theTree.insert(50, 1.5);
      theTree.insert(25, 1.2);
      theTree.insert(75, 1.7);
      theTree.insert(12, 1.5);
      theTree.insert(37, 1.2);
      theTree.insert(43, 1.7);
      theTree.insert(30, 1.5);
      theTree.insert(33, 1.2);
      theTree.insert(87, 1.7);
      theTree.insert(93, 1.5);
      theTree.insert(97, 1.5);

      theTree.displayTree();
      theTree.insert(1, 1.9);
      Node found = theTree.find(12);
      if (found != null) {
         System.out.print("Found: ");
         found.displayNode();
         System.out.print("\n");
      } else
         System.out.print("Could not find ");

      boolean didDelete = theTree.delete(87);
      if (didDelete)
         System.out.print("Deleted \n");
      else
         System.out.print("Could not delete ");

      theTree.traverse(1);
   }

}