Binary tree Java implementation. Simple example.

How to implement a binary tree in Java? That question is one of the most popular in any technical interview. A binary tree is one of the fundamental data structures. That’s why you should learn how to create it. In this lesson, I will show the most straightforward way of implementation.

Example of the binary tree? The step-by-step solution in Java.

To make it easier, let’s divide the process of creation into several basic steps:

• A tree contains small pieces. Those pieces call tree nodes. Try to understand that tree is some amount of that small pieces that are connected in some way. If we try to draw that connection, it will look like a tree. You need to create a class that will include root and two connections left and right;

• The top part of the node contains some data. It can have any type of data. In our case, it will be 10. It calls the root of the node;

• Every node has a left connection. On the left connection, there will be another node. The classic way of the implementation that might be helpful on the technical interview. Is to put fewer numbers on the left and higher numbers on the right. In the left node, we will put 8;

• Every node has the right connection. The same as in the left example, we should connect the top node to another node. And we will put number 12 in it;

• When we search, we will keep in mind that the left side is less than the top (root) right side is more than the top (root). It will help us to work with the data in a tree, like searching for an element;

Animated:

Full code solution:

//Data class for tree node
    private static class TreeNode {
        //TreeNode construction

        //Can be any type of data
        private int data;
        //Left connection
        private TreeNode left;
        //Right connection
        private TreeNode right;

        public TreeNode(int data) {
            this.data = data;
        }
    }

    private TreeNode simpleCreationOfTheTree(){
        //Creating several nodes for a tree
        TreeNode root = new TreeNode(10);
        TreeNode nodeOne = new TreeNode(8);
        TreeNode nodeTwo = new TreeNode(12);
        TreeNode nodeThree = new TreeNode(6);
        TreeNode nodeFour = new TreeNode(14);

        //Manual connecting nodes
        root.left = nodeOne;
        root.right = nodeTwo;
        nodeOne.left = nodeThree;
        nodeTwo.right = nodeFour;
        //Result
        //             root
        //          /         \
        //      nodeOne       nodeTwo
        //      /      \       /   \
        //  nodeThree  null   null  nodeFour

        return root;
    }

In this article, we figured out how to implement binary tree in Java.

Full code and more examples in my facebook group.

Useful links:

• Selection Sort Example
• Bubble Sort Example
• Insertion Sort Example