LLQueue.java

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 */
package pharmcyproject;

/**
 *
 * @author lamees
 */
public class LLQueue<E> {

    static class Node<E> {

        private E element; // reference to the element stored at this node
        private Node<E> next; // reference to the subsequent node in the list

        public Node(E e, Node<E> n) {
            element = e;
            next = n;
        }

        public E getElement() {
            return element;
        }

        public Node<E> getNext() {
            return next;
        }

        public void setNext(Node<E> n) {
            next = n;
        }

        public void setelement(E element) {
            this.element = element;
        }
    }
    protected Node<E> front;
    protected Node<E> rear;
    protected int size;

    public LLQueue() { // constructor
        front = null;
        rear = null;
        size = 0;
    }

    public int size() {
        return size;
    }

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

    public E first() { // returns (but does not remove) the first element
        if (isEmpty()) {
            return null;
        }
        return front.getElement();
    }

    public E last() { // returns (but does not remove) the last element
        if (isEmpty()) {
            return null;
        }
        return rear.getElement();
    }

    public void enqueue(E elem) {
        Node<E> newest = new Node<E>(elem, null);
        if (isEmpty()) {
            front = newest; // special case of a previously empty queue 
        } else {
            rear.setNext(newest); // add node at the tail of the list 
        }
        rear = newest; // update the reference to the tail node 
        size++;
    }

    public E dequeue() {
        if (isEmpty()) {
            return null;
        }
        E answer = front.getElement();
        front = front.getNext();
        size--;
        if (size == 0) {
            rear = null; // the queue is now empty
        }
        return answer;
    }

    public void Display() {
        if (isEmpty()) {
            System.out.println("Queue is empty");
            return;
        }

        int s = size();

        for (int i = 0; i < s; i++) {
            E ele = dequeue();
            System.out.println(ele);

            enqueue(ele);
        }

    }

    public void DisplayPrescription() {
        int s = size();
        for (int i = 0; i < s; i++) {
            Prescription ele = (Prescription) dequeue();
            ele.displayPrescription();
            enqueue((E) ele);
        }
    }

    public void NextPrescription() {

        if (isEmpty()) {
            System.out.println("No prescriptiones.");
        } else {
            Prescription pres = (Prescription) dequeue();
            System.out.println("End of service: ");
            System.out.println(pres);
            System.out.println("The Next prescription is:  ");
            Prescription next = (Prescription) first();
            if(next==null){
                System.out.println("There is no prescription");
            }else{
            System.out.println("The Next prescription is:  ");
            next.displayPrescription();
            }
        }
    }

    public Prescription prescriptionInfo(int id) {

        int s = size();
        Prescription prescription = null;
        for (int i = 0; i < s; i++) {
            Prescription ele = (Prescription) dequeue();
            if (((Prescription) ele).getPrescriptionID() == id) {
                prescription = ele;
            }

            enqueue((E) ele);
        }
        return prescription;

    }
}