Custom implementation of a binary search tree

BinarySearchTree.java

class Main {
    public static void main(String[] args) {
        TreeNode root = new TreeNode(5);
        root.insert(1);
        root.insert(3);
        root.insert(7);
        root.insert(9);
        System.out.println(root.contains(2));
        System.out.println(root.contains(3));
        root.printInOrder();
    }
}

class TreeNode {

    int value;
    TreeNode left;
    TreeNode right;

    public TreeNode() {
    }

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

    public TreeNode(int value, TreeNode left, TreeNode right) {
        this.value = value;
        this.left = left;
        this.right = right;
    }

    public void insert(int val) {

        if (val <= value) {
            if (left != null) {
                left.insert(val);
            } else {
                left = new TreeNode(val);
            }
        } else {
            if (right != null) {
                right.insert(val);
            } else {
                right = new TreeNode(val);
            }
        }
    }

    public boolean contains(int val) {
        if (val == value) {
            return true;
        } else if (val < value) {
            if (left != null) {
                return left.contains(val);
            } else {
                return false;
            }
        } else {
            if (right != null) {
                return right.contains(val);
            } else {
                return false;
            }
        }
    }

    public void printInOrder() {
        if (left != null) {
            left.printInOrder();
        }
        System.out.println(value);
        if (right != null) {
            right.printInOrder();
        }
    }
}