finding a strarting node of a loop.txt

class Main{
    static class Node{
        int data;
        Node next;
        public Node(int data){
            this.data=data;
            this.next=null;
        }
    }
    Node head;
    public void create_loop() {
        Node first = new Node(1);
        Node second = new Node(2);
        Node third = new Node(3);
        Node fourth = new Node(4);
        Node fifth = new Node(5);
        Node sixth = new Node(6);
        head = first;
        first.next=second;
        second.next=third;
        third.next=fourth;
        fourth.next=fifth;
        fifth.next=sixth;
        sixth.next=third;
    }
    public Node detect_a_loop(){
        Node fastPtr=head;
        Node slowPtr=head;
        while (fastPtr!=null&&fastPtr.next!=null){
            fastPtr=fastPtr.next.next;
            slowPtr=slowPtr.next;
            if (fastPtr==slowPtr){
                return getStartingNodeOfLoop(slowPtr);
            }
        }
        return null;
    }

    public Node getStartingNodeOfLoop(Node slowPtr) {
        Node temp=head;
        while (temp!=slowPtr){
            temp=temp.next;
            slowPtr=slowPtr.next;
        }
        return temp;
    }
    public static void main(String[] args){
        Main sl=new Main();
        sl.create_loop();
        System.out.println(sl.detect_a_loop().data);
    }
}