Non-Arg constructor Java

Question

I am calling a constructor in a method to insert new nodes.While I am adding new node default constructor is creating new node with default values . I want to just insert values using insert method as in below code . Is there any way I may avoid first node being default.

class Node {
    Node right, left;
    int data = 0;
    Node() {

    }
    Node(int data) {
        this.data = data;
    }
    public void insert(int value) {
        if (value <= data) {
            if (left == null) {
                left = new Node(value);
            } else {
                left.insert(value);
            }
        } else {
            if (right == null) {
                right = new Node(value);
            } else {
                right.insert(value);
            }
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Node new_node=new Node();//creating first node with 0 value
        new_node.insert(5);
        new_node.insert(4);
        new_node.insert(9);
        new_node.insert(23);
        new_node.insert(70);
        new_node.display();
    }
}

Answer 1

You could use the first value as the first element:

Node new_node = new Node(5); // create 1st node with 1st value

Or you could define a new default constructor with a value that you don't expect to be in the list (let's say -1), but you'd have to be careful about this element in your list that is not really part of the list, and that makes implementing other operations trickier:

Node() { data = -1; }

But all this is symptom of a bigger problem: you shouldn't handle the head of your list in the Node class. It'd be better to create a new class, let's call it MyList and define a Node head attribute on it, and all insert/update/delete/search operations should be implemented on that class.

It's important to keep the head separate, because there will be operations that modify the head. For example, your insert() method doesn't consider the case when the node to insert should go at the beginning of the existing list.