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  1. import java.util.Arrays;
  2. /**
  3.  * Queue Interface that ADT supports
  4.  * @author Prateek
  5.  * @param <T>
  6.  */
  7. interface IQueue<T> {
  8. 	/**
  9. 	 * Inserts an item to Queue, pointed by Rear.
  10. 	 * @param item
  11. 	 */
  12. 	 void enqueue(T item);
  13.  
  14. 	 /**
  15. 	  * @return oldest element in the queue, pointer by front pointer
  16. 	  */
  17. 	 T dequeue();
  18.  
  19. 	 boolean isEmpty();
  20.  
  21. 	 /*return size of Queue*/
  22. 	 int size();
  23.  
  24. 	 boolean isFull();
  25. }
  26.  
  27. /**
  28.  * Circular Queue
  29.  * @author Prateek....
  30.  */
  31. class CircularQueue implements IQueue<Integer>{
  32.  
  33. 	private static final int DEFAULT_CAPACITY = 5;
  34. 	private int N,front,rear;
  35. 	private int[] arr;
  36.  
  37. 	public CircularQueue() {
  38. 		arr = new int[DEFAULT_CAPACITY];
  39. 		N=DEFAULT_CAPACITY;
  40. 		Arrays.fill(arr, -1);
  41. 		front = rear =0;
  42. 	}
  43.  
  44. 	public CircularQueue(int capacity){
  45. 		arr = new int[capacity];
  46. 		N=DEFAULT_CAPACITY;
  47. 		Arrays.fill(arr, -1);
  48. 		front = rear =0;
  49. 	}
  50.  
  51. 	@Override
  52. 	public void enqueue(Integer item) {
  53. 		if(isFull())
  54. 			System.err.println("Stack is Full");
  55. 		else {
  56. 			arr[rear] = item;
  57. 			rear = (rear +1 ) % N;
  58. 		}
  59. 	}
  60.  
  61. 	@Override
  62. 	public Integer dequeue() {
  63. 		if(isEmpty()){
  64. 			System.err.println("Stack is Empty");
  65. 			return null;
  66. 		}
  67. 		else{
  68. 			int val=arr[front];
  69. 			arr[front] = -1;
  70. 			front = (front +1) % N ;
  71. 			return val;
  72. 		}
  73. 	}
  74.  
  75. 	@Override
  76. 	public boolean isEmpty() {
  77. 		return (front == rear) ? true : false;
  78. 	}
  79.  
  80. 	@Override
  81. 	public boolean isFull() {
  82. 		int diff = rear - front;
  83. 		return (diff == N-1 || diff == -1) ? true : false; 
  84. 	}
  85.  
  86. 	@Override
  87. 	public int size() {
  88. 		return (rear > front) ? (rear-front) : (N - (front - rear));
  89. 	}
  90.  
  91. 	/**
  92. 	 * Displays the content of the Queue
  93. 	 */
  94. 	public void display(){
  95. 		int size = size();
  96. 		int index = front;
  97. 		int count=0;
  98.  
  99. 		while(count!=size){
  100. 			System.out.print(arr[index]+"\t");
  101. 		     index = (index + 1) % N;
  102. 		     count++;
  103. 		}
  104. 	}
  105.  
  106. 	public static void main(String[] args) {
  107. 		CircularQueue queue = new CircularQueue();
  108. 		queue.enqueue(1);
  109. 		queue.enqueue(2);
  110. 		queue.enqueue(3);
  111. 		queue.enqueue(4);
  112. 		queue.enqueue(5);
  113. 		queue.enqueue(6);
  114. 		queue.dequeue();
  115. 		queue.dequeue();
  116. 		queue.enqueue(7);
  117. 		queue.display();
  118.  
  119. 	}
  120. }
  121.  
Success #stdin #stdout #stderr 0.07s 380160KB
comments (?)
stdin 
Standard input is empty
stdout 
3	4	7
stderr 
Stack is Full
Stack is Full
https://ideone.com/g6pdG7
Circular Queue
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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