public class Circular_Queue {
static class Node {
int value;
Node link;
}
static class CircularQueue {Node first, last;}
static void Insert(CircularQueue cq, int value) {
Node n = new Node();
n.value = value;
if (cq.first == null) {
cq.first = n;
} else { cq.last .link = n; }
cq.last = n;
cq.last.link = cq.first;
}
static int Delete(CircularQueue cq) {
if (cq.first == null) {
System.out.printf ("Circular Queue is empty");
return Integer.MIN_VALUE;
}
int value;
if (cq.first == cq.last) {
value = cq.first.value;
cq.first = null;
cq.last = null;
} else {
Node n = cq.first;
value = n.value;
cq.first = cq.first.link;
cq.last.link = cq.first;
}
return value ;
}
static void displayCircularQueue( CircularQueue cq) {
Node n = cq.first;
System.out.printf("\nElements in Circular Queue are: ");
while (n.link != cq.first) {
System.out.printf("%d ", n.value);
n = n.link;
}
System.out.printf("%d", n.value);
}
public static void main(String[] args) {
CircularQueue cq = new CircularQueue();
cq.first = cq.last = null;
System.out.println("Inserting value = 69");
Insert(cq, 69);
System.out.println("Inserting value = 12");
Insert(cq, 12);
System.out.println("Inserting value = 42");
Insert(cq, 42);
displayCircularQueue(cq);
System.out.printf("\nDeleting value = %d", Delete(cq));
System.out.printf("\nDeleting value = %d", Delete(cq));
displayCircularQueue(cq);
System.out.println();
System.out.println();
System.out.println("Inserting value = 21");
Insert(cq, 21);
System.out.println("Inserting value = 3");
Insert(cq, 3);
displayCircularQueue(cq);
}
}