Chapter 12, Problem 12PP

Implementation of queue using circular linked list

Program Plan:

Filename: “CircularLinkedQueue.java”

• Define “CircularLinkedQueue” class.
  • Declare variable for reference of first node, rear node and number of items.
  • Default constructor for “CircularLinkedQueue” class.
    • Set front and rear to “null” and count to “0”.
  • Define the method “addToQueue()” with argument of “item”.
    • If “front” is not equal to “null”, then
      • Create a new node using “QueueNode” class.
      • Set the new node as next to rear.
      • Set the new node as rear.
      • Set the new node at last.
        • If the queue is empty, then
        • • Assign the next node to “null” by using “QueueNode” class.
          • Set rear to front for single node in queue.
          • Make the front as next to rear
        • Increment the number of items.
  • Define the method “removeFromQueue()”.
    • If the queue is not empty, then get the element at front node by calling “getQueueElement()” method and eliminate the front node.
      • Update the front and decrement the number of items.
      • Finally returns the resultant element.
        • If the queue is empty, then returns null.
  • Define the method “isEmpty()”.
    • This method returns “true” if the value of “count” is equal to “0”. Otherwise, returns “false”.
  • Define the method “displayQueueValues()”.
    • Declare a variable for node position.
    • Create a reference to front.
    • Performs “while” loop. This loop will repeat to display all elements in queue.
      • Display the element of the queue.
      • Go to the next node by using “getNextNode()” method.

Filename: “QueueNode.java”

• Define “QueueNode” class.
  • Declare required variables for queue elements and next node value.
  • Create default constructor for “QueueNode” class.
    • Assign “null” values for queue elements and next node.
  • Create the parametrized constructor for “QueueNode” class.
  • Define the method “setNextNode()” which is used to set value for next node.
  • Define the method “getNextNode()” which is used to returns the next node value.
  • Define the method “setQueueElement()” which is used to assign value for queue elements.
  • Define the method “getQueueElement()” which is used to returns queue elements.

Filename: “CircularLinkedQueueTest.java”

• Define “CircularLinkedQueueTest” class.
  • Define main function.
    • Create an object “nameQueue” for “CircularLinkedQueueTest” class.
    • Add names to object “nameQueue” by using “addToQueue()” method.
    • Call the method “displayQueueValues()” to display the elements in queue.
    • Remove an element from the queue by calling the method “removeFromQueue()”.
    • Display the result of whether the queue is empty or not by calling the method “isEmpty()”.
    • Display the elements in queue after removing an element from queue by calling the method “displayQueueValues()”.
    • Remove the elements from the queue by calling the method “removeFromQueue()”.
    • Display the result of whether the queue is empty or not by calling the method “isEmpty()”.