Invert a binary tree in java

	package org.enricogiurin.puzzles.varie;
	/**
	* Created by enrico on 12/30/17.
	* https://www.programcreek.com/2014/06/leetcode-invert-binary-tree-java/
	*/
	public class BinaryTree<T extends Comparable> {
	private BinaryTree<T> left;
	private BinaryTree<T> right;
	private T value;
	public BinaryTree(T value){
	this.value = value;
	}
	public void add(T value){
	if(value==null){
	return;
	}
	add(value, this);
	}
	private void add(T value, BinaryTree binaryTree){
	if(value.compareTo(binaryTree.value) <= 0) {
	//insert left
	if(binaryTree.left == null){
	binaryTree.left = new BinaryTree(value);
	}else{
	add(value, binaryTree.left);
	}
	}else{
	//insert right
	if(binaryTree.right == null){
	binaryTree.right = new BinaryTree(value);
	}
	else{
	add(value, binaryTree.right);
	}
	}
	}
	public void printBinaryTree(BinaryTree binaryTree) {
	System.out.println(binaryTree.value);
	if(binaryTree.left != null){
	printBinaryTree(binaryTree.left);
	}
	if(binaryTree.right != null){
	printBinaryTree(binaryTree.right);
	}
	}
	public void invert() {
	invert(this);
	}
	private void invert(BinaryTree binaryTree){
	BinaryTree tmp = binaryTree.left;
	binaryTree.left = binaryTree.right;
	binaryTree.right = tmp;
	if(binaryTree.left!=null){
	invert(binaryTree.left);
	}
	if(binaryTree.right!=null){
	invert(binaryTree.right);
	}
	}
	public static void main(String[] args) {
	BinaryTree<Integer> binaryTree = new BinaryTree<>(5);
	binaryTree.add(2);
	binaryTree.add(7);
	binaryTree.add(9);
	binaryTree.add(6);
	binaryTree.printBinaryTree(binaryTree);
	binaryTree.invert();
	System.out.println("*****");
	binaryTree.printBinaryTree(binaryTree);
	}
	}

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