In this source code example, we will write a Java program to demonstrate how to implement a circular linked list in Java.

Circular Linked List Implementation in Java - Source Code

import java.util.NoSuchElementException;

public class CircularLinkedList {
   private ListNode last;
   private int length;

   private class ListNode {
      private ListNode next;
      private int data;

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

   public CircularLinkedList() {
      last = null;
      length = 0;
   }

   public int length() {
      return length;
   }

   public boolean isEmpty() {
      return length == 0;
   }

   public void createCircularLinkedList() {
      ListNode first = new ListNode(1);
      ListNode second = new ListNode(5);
      ListNode third = new ListNode(10);
      ListNode fourth = new ListNode(15);

      first.next = second;
      second.next = third;
      third.next = fourth;
      fourth.next = first;

      last = fourth;
   }

   public void display() {
      if (last == null) {
         return;
      }

      ListNode first = last.next;
      while (first != last) {
         System.out.print(first.data + " --> ");
         first = first.next;
      }
      System.out.println(first.data);
   }

   public void insertFirst(int data) {
      ListNode temp = new ListNode(data);
      if (last == null) {
         last = temp;
      } else {
         temp.next = last.next;
      }
      last.next = temp;
      length++;
   }

   public void insertLast(int data) {
      ListNode temp = new ListNode(data);
      if (last == null) {
         last = temp;
         last.next = last;
      } else {
         temp.next = last.next;
         last.next = temp;
         last = temp;
      }
      length++;
   }

   public ListNode removeFirst() {
      if (isEmpty()) {
         throw new NoSuchElementException("Circular Singly Linked List is already empty");
      }

      ListNode temp = last.next;
      if (last.next == last) {
         last = null;
      } else {
         last.next = temp.next;
      }
      temp.next = null;
      length--;
      return temp;
   }

   public static void main(String[] args) {
      CircularLinkedList cll = new CircularLinkedList();
      cll.createCircularLinkedList();
      cll.display();
   }
}

Output:

1 --> 5 --> 10 --> 15