Class ObjectArrayFIFOQueue<K>

  • All Implemented Interfaces:
    PriorityQueue<K>, java.io.Serializable

    public class ObjectArrayFIFOQueue<K>
    extends java.lang.Object
    implements PriorityQueue<K>, java.io.Serializable
    A type-specific array-based FIFO queue, supporting also deque operations.

    Instances of this class represent a FIFO queue using a backing array in a circular way. The array is enlarged and shrunk as needed. You can use the trim() method to reduce its memory usage, if necessary.

    This class provides additional methods that implement a deque (double-ended queue).

    See Also:
    Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int INITIAL_CAPACITY
      The standard initial capacity of a queue.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()
      Removes all elements from this queue.
      java.util.Comparator<? super K> comparator()
      Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
      K dequeue()
      Dequeues the first element from the queue.
      K dequeueLast()
      Dequeues the last element from the queue.
      void enqueue​(K x)
      Enqueues a new element.
      void enqueueFirst​(K x)
      Enqueues a new element as the first element (in dequeuing order) of the queue.
      K first()
      Returns the first element of the queue.
      K last()
      Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).
      int size()
      Returns the number of elements in this queue.
      void trim()
      Trims the queue to the smallest possible size.
      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • INITIAL_CAPACITY

        public static final int INITIAL_CAPACITY
        The standard initial capacity of a queue.
        See Also:
        Constant Field Values
    • Constructor Detail

      • ObjectArrayFIFOQueue

        public ObjectArrayFIFOQueue​(int capacity)
        Creates a new empty queue with given capacity.
        Parameters:
        capacity - the initial capacity of this queue.
      • ObjectArrayFIFOQueue

        public ObjectArrayFIFOQueue()
        Creates a new empty queue with standard initial capacity.
    • Method Detail

      • comparator

        public java.util.Comparator<? super K> comparator()
        Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
        Specified by:
        comparator in interface PriorityQueue<K>
        Returns:
        the comparator associated with this sorted set, or null if it uses its elements' natural ordering.
        Implementation Specification:
        This implementation returns null (FIFO queues have no comparator).
      • dequeue

        public K dequeue()
        Description copied from interface: PriorityQueue
        Dequeues the first element from the queue.
        Specified by:
        dequeue in interface PriorityQueue<K>
        Returns:
        the dequeued element.
      • dequeueLast

        public K dequeueLast()
        Dequeues the last element from the queue.
        Returns:
        the dequeued element.
        Throws:
        java.util.NoSuchElementException - if the queue is empty.
      • enqueue

        public void enqueue​(K x)
        Description copied from interface: PriorityQueue
        Enqueues a new element.
        Specified by:
        enqueue in interface PriorityQueue<K>
        Parameters:
        x - the element to enqueue.
      • enqueueFirst

        public void enqueueFirst​(K x)
        Enqueues a new element as the first element (in dequeuing order) of the queue.
        Parameters:
        x - the element to enqueue.
      • first

        public K first()
        Description copied from interface: PriorityQueue
        Returns the first element of the queue.
        Specified by:
        first in interface PriorityQueue<K>
        Returns:
        the first element.
      • last

        public K last()
        Description copied from interface: PriorityQueue
        Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).

        This default implementation just throws an UnsupportedOperationException.

        Specified by:
        last in interface PriorityQueue<K>
        Returns:
        the last element.
      • clear

        public void clear()
        Description copied from interface: PriorityQueue
        Removes all elements from this queue.
        Specified by:
        clear in interface PriorityQueue<K>
      • trim

        public void trim()
        Trims the queue to the smallest possible size.
      • size

        public int size()
        Description copied from interface: PriorityQueue
        Returns the number of elements in this queue.
        Specified by:
        size in interface PriorityQueue<K>
        Returns:
        the number of elements in this queue.