System.out.println ( "\n\nPreorder traversal" );
tree.preorderTraversal(); // perform preorder traversal of tree
System.out.println ( "\n\nInorder traversal" );
tree.inorderTraversal(); // perform inorder traversal of tree
System.out.println ( "\n\nPostorder traversal" );
tree.postorderTraversal(); // perform postorder traversal of tree
System.out.println();
} // end main