CircularLinkedListCheck.java

// This the structure of Linked list node 
class Node {
    int data;
    Node next;
    public Node(int data){
        this.data = data;
        this.next = null;
    }
}

// This class for checking the whether linked list is circlular or not 
// This method method will use FLOYED NUMBER THEORY
class CircularLinkedListCheck {
    // public static void main(String[] args){
    //     // Configuring a circular linked list 
    //     var root = new Node(00);
    //     Node node1 = new Node(10);
    //     root.next = node1;
    //     Node node2 = new Node(20);
    //     node1.next = node2;
    //     Node node3 = new Node(30);
    //     node2.next = node3;
    //     Node node4 = new Node(40);
    //     node3.next = node4;
    //     Node node5 = new Node(50);
    //     node4.next = node5;
    //     Node node6 = new Node(60);
    //     node5.next = node6;
    //     node6.next = node3;
    //     isCircular(root);
    // }

    public static void isCircular(Node head){
        // Covering the default case 
        if (head == null || head.next == null){
            System.out.println("This is not a circular linked list");
        }

        //creating pointers 
        Node fastPtr = head;
        Node slowPtr = head;
        Boolean isCircle = false;
        while(fastPtr != null || fastPtr.next != null){ 
            slowPtr = slowPtr.next;
            fastPtr = fastPtr.next.next; 
            if (fastPtr == slowPtr){
                isCircle = true;
                break;
            }
        }
        System.out.println(isCircle ? "This is a circular linked list" : "This is not a circular linked list");

        // Find the origin of loop
        slowPtr = head;
        while(slowPtr != fastPtr){
            slowPtr = slowPtr.next;
            fastPtr = fastPtr.next;
        }
        System.out.println(slowPtr.data);
    }

}