Stacks and Queues - Advanced Topics in Java: Core Concepts in Data Structures - page 133

Program P4.7
import java.util.*;
public class QueueTest {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
Queue Q = new Queue();
System.out.printf("Enter a positive integer: ");
int n = in.nextInt();
while (n > 0) {
Q.enqueue(n % 10);
n = n / 10;
}
System.out.printf("\nDigits in reverse order: ");
while (!Q.empty())
System.out.printf("%d", Q.dequeue());
System.out.printf("\n");
} //end main
} //end QueueTest
class Queue {
final static int MaxQ = 100;
int head = 0, tail = 0;
int[] QA = new int[MaxQ];
public boolean empty() {
return head == tail;
}
public void enqueue(int n) {
tail = (tail + 1) % MaxQ; //increment tail circularly
if (tail == head) {
System.out.printf("\nQueue is full\n");
System.exit(1);
}
QA[tail] = n;
} //end enqueue
public int dequeue() {
if (this.empty()) {
System.out.printf("\nAttempt to remove from an empty queue\n");
System.exit(2);
}
head = (head + 1) % MaxQ; //increment head circularly
return QA[head];
} //end dequeue
} //end class Queue