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  1. class Main {
  2. 	public static void main (String[] args) {
  3.         class Node<T> {
  4.             T payload;
  5.             Node<T> next;
  6.             Node<T> prev;
  7.             public Node(T payload) {
  8.                 this.payload = java.util.Objects.requireNonNull(payload);
  9.             }
  10.         }
  11.         class Tunnel<T> {
  12.             boolean hasExit;
  13.             Node<T> head;
  14.             Node<T> tail;
  15.             public void add(T t) {
  16.                 Node<T> node = new Node<>(t);
  17.                 if (head == null) {
  18.                     head = node;
  19.                 } else {
  20.                     tail.next = node;
  21.                     node.prev = tail;
  22.                 }
  23.                 tail = node;
  24.             }
  25.             public T remove() {
  26.                 if (head == null) {
  27.                     return null;
  28.                 }
  29.                 if (hasExit) {
  30.                     Node<T> temp = head;
  31.                     if (head.next == null) {
  32.                         tail = null;
  33.                     } else {
  34.                         head.next.prev = null;
  35.                     }
  36.                     head = head.next;
  37.                     return temp.payload;
  38.                 } else {
  39.                     Node<T> temp = tail;
  40.                     if (head.next == null) {
  41.                         head = null;
  42.                     } else {
  43.                         tail.prev.next = null;
  44.                     }
  45.                     tail = tail.prev;
  46.                     return temp.payload;
  47.                 }
  48.             }
  49.         }
  50.         Tunnel<String> t = new Tunnel<>();
  51.         t.hasExit = true;
  52.         t.add("Hugo");
  53.         t.add("Paco");
  54.         t.add("Luis");
  55.         System.out.println(t.remove());
  56.         System.out.println(t.remove());
  57.         t.hasExit = false;
  58.         System.out.println("¡Sin salida!");
  59.         t.add("Juan");
  60.         t.add("Olga");
  61.         t.add("Ciro");
  62.         for(String child; (child = t.remove()) != null;) {
  63.             System.out.println(child);
  64.         }
  65. 	}
  66. }
Success #stdin #stdout 0.1s 320320KB
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Standard input is empty
stdout
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Hugo
Paco
¡Sin salida!
Ciro
Olga
Juan
Luis
https://ideone.com/U6zvJI
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
public

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