queue

class Queue {
private final int MAX;
private int[] intArray;
private int front;
private int rear;
private int itemCount;

public Queue(int size){
MAX = size;
intArray = new int[MAX];
front = 0;
rear = -1;
itemCount = 0;
}

public void insert(int data){
if(!isFull()){
if(rear == MAX-1){
rear = -1;
}

     intArray[++rear] = data;
     itemCount++;
  }

}

public int remove(){
int data = intArray[front++];
if(front == MAX){
front = 0;
}
itemCount--;
return data;
}

public int peek(){
return intArray[front];
}

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

public boolean isFull(){
return itemCount == MAX;
}

public int size(){
return itemCount;
}
}

public class QueueDemo {
public static void main(String[] args){
Queue queue = new Queue(6);

      //insert 5 items
      queue.insert(3);
      queue.insert(5);
      queue.insert(9);
      queue.insert(1);
      queue.insert(12);

      // front : 0
      // rear  : 4
      // ------------------
      // index : 0 1 2 3 4 
      // ------------------
      // queue : 3 5 9 1 12

      queue.insert(15);

      // front : 0
      // rear  : 5
      // ---------------------
      // index : 0 1 2 3 4  5 
      // ---------------------
      // queue : 3 5 9 1 12 15

      if(queue.isFull()){
         System.out.println("Queue is full!");   
      }


      //remove one item
      int num = queue.remove();
      System.out.println("Element removed: "+num);
      // front : 1
      // rear  : 5
      // -------------------
      // index : 1 2 3 4  5
      // -------------------
      // queue : 5 9 1 12 15

      //insert more items
      queue.insert(16);

      // front : 1
      // rear  : -1
      // ----------------------
      // index : 0  1 2 3 4  5
      // ----------------------
      // queue : 16 5 9 1 12 15

      //As queue is full, elements will not be inserted.
      queue.insert(17);
      queue.insert(18);
 
      // ----------------------
      // index : 0  1 2 3 4  5
      // ----------------------
      // queue : 16 5 9 1 12 15
      System.out.println("Element at front: "+queue.peek());

      System.out.println("----------------------");
      System.out.println("index : 5 4 3 2  1  0");
      System.out.println("----------------------");
      System.out.print("Queue:  ");
      while(!queue.isEmpty()){
         int n = queue.remove();            
         System.out.print(n +" ");
      }
   }
}