public boolean insert(int elem) {TreeNode node = new TreeNode(elem);if (null == this.root) {this.root = node;return true;} else {return insertChild(this.root, node);}}    /*** insert the newNode to the child position of parent node* @param parent* @param newNode* @return true if the newNode insert successfully or false if the newNode have been exist*/private boolean insertChild(TreeNode parent, TreeNode newNode) {if (parent.getElem() == newNode.getElem()) {return false;} else if (parent.getElem() > newNode.getElem()) {if (null  == parent.getLeft()) {parent.setLeft(newNode);newNode.setParent(parent);return true;} else {return insertChild(parent.getLeft(), newNode);}} else {if (null == parent.getRight()) {parent.setRight(newNode);newNode.setParent(parent);return true;} else {return insertChild(parent.getRight(), newNode);}}}

    /*** delete the node which element equals to parameter elem* @param elem* @return true if the node can be found and delete otherwise false*/public boolean delete(int elem) {if (null == this.root) {return false;} else {TreeNode node = this.root;// find out the node need to be deletedwhile (null != node) {if (node.getElem() == elem) {deleteNode(node);return true;} else if (node.getElem() > elem) {node = node.getLeft();} else {node = node.getRight();}}return false;}}private void deleteNode(TreeNode node) {if (null == node.getLeft() && null == node.getRight()) {// deleted node is a leaveif (null  == node.getParent()) {// deleted node is rootthis.root = null;} else if (node == node.getParent().getLeft()) {// deleted node is the left child of its parentnode.getParent().setLeft(null);} else {// deleted node is the right child of its parentnode.getParent().setRight(null);}} else if (null == node.getLeft()) {// deleted node only hae right childif (null  == node.getParent()) {this.root = node.getRight();} else if (node == node.getParent().getLeft()) {node.getParent().setLeft(node.getRight());} else {node.getParent().setRight(node.getRight());}node.getRight().setParent(node.getParent());} else if (null == node.getRight()) {// deleted node only have left childif (null  == node.getParent()) {this.root = node.getLeft();} else if (node == node.getParent().getLeft()) {node.getParent().setLeft(node.getLeft());} else {node.getParent().setRight(node.getLeft());}node.getLeft().setParent(node.getParent());} else {// deleted node have both left & right children// find out the precursor of deleted node// the precursor node replace the position of deleted nodeTreeNode pre = node.getLeft();while (null != pre.getRight()) {pre  = pre.getRight();}// swap the elem of precursor node and deleted node// then delete the precursor node
            TreeUtils.swapTreeElem(pre, node);deleteNode(pre);}}

1. insert
2. delete
3. search
4. print
5. exit
->1
->10 5 2 7 6 18 13 -1
insert success

1. insert
2. delete
3. search
4. print
5. exit
->4
-1813
107652
-

1. insert
2. delete
3. search
4. print
5. exit
->2
->5
delete success
--------------------------------------------------------------
1. insert
2. delete
3. search
4. print
5. exit
->4
-1813
10762
-