AppointmentQueue.java

/*
 * Click nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to change this license
 * Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Class.java to edit this template
 */
package hospitalmanagementsystem;




public class AppointmentQueue {
    
    // INNER CLASS: QueueNode
    class QueueNode {
        Appointment data;
        QueueNode next;

        public QueueNode(Appointment data) {
            this.data = data;
            this.next = null;
        }
    }
    
    private QueueNode front;
    private QueueNode rear;

    public AppointmentQueue() {
        this.front = null;
        this.rear = null;
    }

    public boolean isEmpty() {
        return front == null;
    }

    // Adds a new appointment to the end of the queue.
    // Critical for maintaining fair, First-Come-First-Served order for doctor visits.
    // Time Complexity: O(1) (Direct access via 'rear' pointer)
    public void enqueue(Appointment appointment) {
        QueueNode newNode = new QueueNode(appointment);
        if (rear != null) {
            rear.next = newNode;
        }
        rear = newNode;   
        if (front == null) {
            front = newNode;
        }
    }

    // Removes and returns the appointment at the front of the queue.
    // Used when the doctor is ready to examine the next patient.
    // Time Complexity: O(1) (Direct access via 'front' pointer)
    public Appointment dequeue() {
        if (isEmpty()) {
            return null;
        }
        
        Appointment data = front.data;
        front = front.next;
        if (front == null) {
            rear = null;
        }
        return data;
    }

    // Traverses the queue to display all waiting patients in order.
    // Useful for showing the doctor how many patients are waiting.
    public void display() {
        if (isEmpty()) {
            System.out.println("  Queue is empty.");
            return;
        }
        QueueNode current = front;
        
        int position = 1;
        while (current != null) {
            
            System.out.println("  " + position + ". " + current.data);
            current = current.next;
            position++;
        }
    }
    
    
    public int size() {
        if (isEmpty()) return 0;
        
        int count = 0;
        QueueNode current = front;
        while (current != null) {
            count++;
            current = current.next;
        }
        return count;
    }
    
    public QueueNode getFront() {
        return front;
    }
    
    public void setFront(QueueNode front) {
        this.front = front;
    }

    public void setRear(QueueNode rear) {
        this.rear = rear;
    }
    
    
}