RAUL-SUAREZ

tp3-queue

Oct 25th, 2021
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  1. //
  2. // Created by Julio Tentor <jtentor@fi.unju.edu.ar>
  3. //
  4.  
  5. /*
  6. public interface Queue<E>
  7. extends Collection<E>
  8.  
  9. A collection designed for holding elements prior to processing.
  10. Besides basic Collection operations, queues provide additional insertion,
  11. extraction, and inspection operations. Each of these methods exists in
  12. two forms: one throws an exception if the operation fails, the other
  13. returns a special value (either null or false, depending on the operation).
  14.  
  15. The latter form of the insert operation is designed specifically for use
  16. with capacity-restricted Queue implementations; in most implementations,
  17. insert operations cannot fail.
  18.  
  19. Queues typically, but do not necessarily, order elements in a FIFO
  20. (first-in-first-out) manner. Among the exceptions are priority queues,
  21. which order elements according to a supplied comparator, or the elements'
  22. natural ordering, and LIFO queues (or stacks) which order the elements
  23. LIFO (last-in-first-out). Whatever the ordering used, the head of the
  24. queue is that element which would be removed by a call to remove() or
  25. poll(). In a FIFO queue, all new elements are inserted at the tail of
  26. the queue. Other kinds of queues may use different placement rules.
  27. Every Queue implementation must specify its ordering properties.
  28.  
  29. The offer method inserts an element if possible, otherwise returning
  30. false. This differs from the Collection.add method, which can fail to
  31. add an element only by throwing an unchecked exception. The offer
  32. method is designed for use when failure is a normal, rather than
  33. exceptional occurrence, for example, in fixed-capacity (or "bounded")
  34. queues.
  35.  
  36. The remove() and poll() methods remove and return the head of the queue.
  37. Exactly which element is removed from the queue is a function of the
  38. queue's ordering policy, which differs from implementation to
  39. implementation. The remove() and poll() methods differ only in their
  40. behavior when the queue is empty: the remove() method throws an
  41. exception, while the poll() method returns null.
  42.  
  43. The element() and peek() methods return, but do not remove, the head
  44. of the queue.
  45.  
  46. The Queue interface does not define the blocking queue methods, which
  47. are common in concurrent programming. These methods, which wait for
  48. elements to appear or for space to become available, are defined in
  49. the BlockingQueue interface, which extends this interface.
  50.  
  51. Queue implementations generally do not allow insertion of null elements,
  52. although some implementations, such as LinkedList, do not prohibit
  53. insertion of null. Even in the implementations that permit it, null
  54. should not be inserted into a Queue, as null is also used as a special
  55. return value by the poll method to indicate that the queue contains no
  56. elements.
  57.  
  58. Queue implementations generally do not define element-based versions of
  59. methods equals and hashCode but instead inherit the identity based
  60. versions from class Object, because element-based equality is not
  61. always well-defined for queues with the same elements but different
  62. ordering properties.
  63.  
  64. This interface is a member of the Java Collections Framework.
  65.  
  66.  
  67.  
  68. from https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/util/Queue.html
  69. from https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/util/Queue.html
  70. from https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/util/Queue.html
  71.  
  72.  */
  73.  
  74.  
  75. import java.util.Arrays;
  76.  
  77. public class Queue<ELEMENT> {
  78.  
  79.     //region Constants
  80.  
  81.     private final static Integer defaulDimension = 10;
  82.  
  83.     //endregion
  84.  
  85.     //region Attributes
  86.  
  87.     private ELEMENT [] data;
  88.     private int head;
  89.     private int tail;
  90.     private int count;
  91.  
  92.     //endregion
  93.  
  94.     //region Constructors
  95.  
  96.     public Queue() {
  97.         this(Queue.defaulDimension);
  98.     }
  99.     public Queue(int dimension) {
  100.         this.data = (ELEMENT[]) new Object[dimension];
  101.         this.head = 0;
  102.         this.tail = 0;
  103.         this.count = 0;
  104.     }
  105.     //endregion
  106.  
  107.     //region Queue Internal Methods
  108.     private int next(int pos) {
  109.         if (++pos >= this.data.length) {
  110.             pos = 0;
  111.         }
  112.         return pos;
  113.     }
  114.     //endregion
  115.  
  116.  
  117.     //region Queue Methods
  118.  
  119.     // Operacion EnQueue en la teoría de Estructura de Datos
  120.     //
  121.     // Inserts the specified element into this queue if it is possible to do so
  122.     // immediately without violating capacity restrictions, returning true upon
  123.     // success and throwing an IllegalStateException if no space is currently
  124.     // available.
  125.     public boolean add(ELEMENT element) {
  126.  
  127.         if (this.size() >= this.data.length) {
  128.             throw new IllegalStateException("Cola llena ...");
  129.         }
  130.  
  131.         this.data[this.tail] = element;
  132.         this.tail = this.next(this.tail);
  133.         ++this.count;
  134.  
  135.         return true;
  136.     }
  137.  
  138.     // Operacion peek en la teoría de Estructura de Datos
  139.     //
  140.     // Retrieves, but does not remove, the head of this queue. This method differs
  141.     // from peek only in that it throws an exception if this queue is empty.
  142.     public ELEMENT element() {
  143.  
  144.         if (this.size() <= 0) {
  145.             throw new IllegalStateException("Cola vacía ...");
  146.         }
  147.  
  148.         return this.data[this.head];
  149.     }
  150.  
  151.     // Operacion EnQueue en la teoría de Estructura de Datos
  152.     //
  153.     // Inserts the specified element into this queue if it is possible to do so
  154.     // immediately without violating capacity restrictions. When using a
  155.     // capacity-restricted queue, this method is generally preferable to add(E),
  156.     // which can fail to insert an element only by throwing an exception.
  157.     public boolean offer(ELEMENT element) {
  158.  
  159.         if (this.size() >= this.data.length) {
  160.             return false;
  161.         }
  162.  
  163.         this.data[this.tail] = element;
  164.         this.tail = this.next(this.tail);
  165.         ++this.count;
  166.  
  167.         return true;
  168.     }
  169.  
  170.     // Retrieves, but does not remove, the head of this queue, or returns null if
  171.     // this queue is empty.
  172.     public ELEMENT peek() {
  173.         if (this.size() <= 0) {
  174.             return null;
  175.         }
  176.  
  177.         return this.data[this.head];
  178.     }
  179.  
  180.     // Operacion DeQueue en la teoría de Estructura de Datos
  181.     //
  182.     // Retrieves and removes the head of this queue, or returns null if this queue
  183.     // is empty.
  184.     public ELEMENT pool() {
  185.         if (this.size() <= 0) {
  186.             return null;
  187.         }
  188.  
  189.         ELEMENT result = this.data[this.head];
  190.         this.head = this.next(this.head);
  191.         --this.count;
  192.  
  193.         return result;
  194.     }
  195.  
  196.     // Operacion DeQueue en la teoría de Estructura de Datos
  197.     //
  198.     // Retrieves and removes the head of this queue. This method differs from poll()
  199.     // only in that it throws an exception if this queue is empty.
  200.     public ELEMENT remove() {
  201.         if (this.size() <= 0) {
  202.             throw new IllegalStateException("Cola vacía ...");
  203.         }
  204.  
  205.         ELEMENT result = this.data[this.head];
  206.         this.head = this.next(this.head);
  207.         --this.count;
  208.  
  209.         return result;
  210.     }
  211.     //endregion
  212.  
  213.  
  214.     //region Override Object basic methods
  215.  
  216.     @Override
  217.     public String toString() {
  218.  
  219.         if (this.size() <=0) {
  220.             return "";
  221.         }
  222.  
  223.         // from https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/lang/StringBuilder.html
  224.         StringBuilder sb = new StringBuilder();
  225.         sb.append("[" + this.data[this.head].toString());
  226.  
  227.         for (int cta = 1, pos = this.next(this.head); cta < this.size(); ++cta, pos = this.next(pos)) {
  228.             sb.append(", " + this.data[pos].toString());
  229.         }
  230.  
  231.         sb.append("]");
  232.         return sb.toString();
  233.     }
  234.     //endregion
  235.  
  236.  
  237.     //region Collection Methods
  238.  
  239.     public boolean isEmpty() {
  240.         return this.count <= 0;
  241.     }
  242.  
  243.     public int size() {
  244.         return this.count;
  245.     }
  246.  
  247.     public Object[] toArray() {
  248.         Object[] result = new Object[this.count];
  249.         for(int i = 0, pos = this.head, cta = this.size(); cta > 0; ++i, pos = this.next(pos), --cta) {
  250.             result[i] = this.data[pos];
  251.         }
  252.         return result;
  253.     }
  254.     //endregion
  255.  
  256.  
  257.     //region Caso Ejemplo b) Methods
  258.  
  259.     public static Queue<Object> union(Queue<?> stack1, Queue<?> stack2) {
  260.  
  261.         Queue<Object> result = new Queue<Object>(stack1.size() + stack2.size());
  262.  
  263.         for(int pos = stack1.head, cta = stack1.size(); cta > 0; pos = stack1.next(pos), --cta) {
  264.             result.offer( stack1.data[pos] );
  265.         }
  266.         for(int pos = stack2.head, cta = stack2.size(); cta > 0; pos = stack2.next(pos), --cta) {
  267.             result.offer( stack2.data[pos] );
  268.         }
  269.  
  270.         return result;
  271.     }
  272.  
  273.     public Queue<Object> union(Queue<?> stack2) {
  274.         return Queue.union(this, stack2);
  275.     }
  276.     //endregion
  277.  
  278. }
  279.  
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