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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class GenericQueue<Item> implements Iterable<Item> {
  6. 	private Node first, last;
  7.  
  8. 	private class Node {
  9. 		Item item;
  10. 		Node next;
  11. 	}
  12.  
  13. 	public boolean isEmpty() {
  14. 		return first == null;
  15. 	}
  16.  
  17. 	public void enqueue(Item item) {
  18. 		Node oldLast = last;
  19. 		last = new Node();
  20. 		last.item = item;
  21. 		last.next = null;
  22. 		if (isEmpty()) first = last;
  23. 		else oldLast.next = last;
  24. 	}
  25.  
  26. 	public Item dequeue() {
  27. 		Item item = first.item;
  28. 		first = first.next;
  29. 		if (isEmpty()) last = null;
  30. 		return item;
  31. 	}
  32.  
  33. 	@Override
  34. 	public Iterator<Item> iterator() {
  35. 		return new LinkedIterator();
  36. 	}
  37.  
  38. 	private class LinkedIterator implements Iterator<Item> {
  39. 		private Node current = first;
  40.  
  41. 		public boolean hasNext() {
  42. 			return current != null;
  43. 		}
  44.  
  45. 		public Item next() {
  46. 			if (!hasNext()) throw new NoSuchElementException();
  47. 			Item item = current.item;
  48. 			current = current.next;
  49. 			return item;
  50. 		}
  51. 	}
  52. }
  53.  
  54. public class Main {
  55. 	public static void main(String[] args) throws java.lang.Exception {
  56. 		GenericQueue<String> strQ = new GenericQueue<>();
  57. 		strQ.enqueue("Cat");
  58. 		strQ.enqueue("Dog");
  59.  
  60. 		System.out.println("Iterating:");
  61. 		for (String s : strQ) System.out.println(s);
  62.  
  63. 		System.out.println("Dequeuing:");
  64. 		System.out.println(strQ.dequeue());
  65. 		System.out.println(strQ.dequeue());
  66. 	}
  67. }
  68.  
Success #stdin #stdout 0.09s 54440KB
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Standard input is empty
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Iterating:
Cat
Dog
Dequeuing:
Cat
Dog
https://ideone.com/DmsN7M
language:
Java (HotSpot 12)
created:
1 day ago
visibility:
public

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