DS: Circular Queue

import java.util.Scanner;

public class CQueue {
 public static void main(String args[]) {

  Scanner s = new Scanner(System.in);
  int choice, n;
  Object value;
  System.out.println("Enter a size");
  n = s.nextInt();

  List c = new List(n);
  do {
   System.out
     .println("CQueue operations\n1.puts()\n2.remove()\n3.getfrontelement()\n4.getrearelement()\n5.empty()\n6.size()\n7.display()\nEnter ur choice");
   choice = s.nextInt();
   switch (choice) {
   case 1:
    System.out.println("Enter a value");
    value = s.nextInt();
    c.puts(value);
    break;
   case 2:
    System.out.println("The deleted element is=" + c.remove());
    break;
   case 3:
    System.out.println("The front element is=" + c.front_element());
    break;
   case 4:
    System.out.println("The rear element is=" + c.rear_element());
    break;
   case 5:
    if (c.isempty())
     System.out.println("CQueue is not empty");
    else
     System.out.println("CQueue is not empty");
    break;
   case 6:
    System.out.println("The size is=" + c.size());
    break;
   case 7:
    System.out.println("The elements in the queue is=" + c);
    break;
   }
  } while (choice < 8);

 }
}

class List {
 int front, rear;
 Object x[];
 int size = 0;

 public List(int y) {
  front = -1;
  rear = -1;
  x = new Object[y];

 }

 public int size() {
  return size;
 }

 public boolean isempty() {
  return front == -1;
 }

 public void puts(Object value) {

  Scanner s = new Scanner(System.in);
  if (rear == x.length - 1)
   rear = 0;
  else
   rear++;
  if (front == rear) {
   if (rear == 0)
    rear = x.length - 1;
   else
    rear--;

   System.out.println("Queue is overflow");
   return;
  } else {
   if (front == -1)
    front = 0;
   x[rear] = value;
  }
  size++;
 }

 public Object remove() {

  if (front == -1) {
   System.out.println("Queue is underflow");
   return null;
  }
  Object value = x[front];
  x[front] = null;
  if (front == rear) {
   front = rear = -1;

  } else {
   if (front == x.length - 1)
    front = 0;
   else
    front++;
  }
  size--;
  return value;

 }

 public String toString() {
  StringBuffer y = new StringBuffer("[");
  if (front < rear) {
   for (int i = front; i <= rear; i++) {
    if (x[i] == (Object) 0)
     y.append("null,");
    else
     y.append(x[i] + " ");

   }
  } else {
   for (int i = front; i < x.length; i++) {
    if (x[i] == (Object) 0)
     y.append("null,");
    else
     y.append(x[i] + " ");

   }

   for (int i = 0; i <= rear; i++) {
    if (x[i] == (Object) 0)
     y.append("null,");
    else
     y.append(x[i] + ", ");

   }

  }
  y.append("]");
  return new String(y);

 }

 public Object front_element() {
  if (front == -1) {
   System.out.println("Queue is underflow");
   return null;

  }
  return x[front];

 }

 public Object rear_element() {
  if (front == -1) {
   System.out.println("Queue is underflow");
   return null;

  }
  return x[rear];

 }
}