Class PriorityQueues.EmptyPriorityQueue

  • All Implemented Interfaces:
    PriorityQueue, java.io.Serializable
    Enclosing class:
    PriorityQueues

    public static class PriorityQueues.EmptyPriorityQueue
    extends java.lang.Object
    implements PriorityQueue, java.io.Serializable
    An immutable class representing the empty priority queue.

    This class may be useful to implement your own in case you subclass PriorityQueue.

    See Also:
    Serialized Form
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void changed()
      Notifies the queue that the first element has changed (optional operation).
      void clear()
      Removes all elements from this queue.
      java.lang.Object clone()  
      java.util.Comparator<?> comparator()
      Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
      java.lang.Object dequeue()
      Dequeues the first element from the queue.
      void enqueue​(java.lang.Object o)
      Enqueues a new element.
      boolean equals​(java.lang.Object o)  
      java.lang.Object first()
      Returns the first element of the queue.
      int hashCode()  
      boolean isEmpty()
      Checks whether this queue is empty.
      java.lang.Object 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.
      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, toString, wait, wait, wait
    • Method Detail

      • enqueue

        public void enqueue​(java.lang.Object o)
        Description copied from interface: PriorityQueue
        Enqueues a new element.
        Specified by:
        enqueue in interface PriorityQueue
        Parameters:
        o - the element to enqueue.
      • dequeue

        public java.lang.Object dequeue()
        Description copied from interface: PriorityQueue
        Dequeues the first element from the queue.
        Specified by:
        dequeue in interface PriorityQueue
        Returns:
        the dequeued element.
      • isEmpty

        public boolean isEmpty()
        Description copied from interface: PriorityQueue
        Checks whether this queue is empty.

        This default implementation checks whether PriorityQueue.size() is zero.

        Specified by:
        isEmpty in interface PriorityQueue
        Returns:
        true if this queue is empty.
      • size

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

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

        public java.lang.Object first()
        Description copied from interface: PriorityQueue
        Returns the first element of the queue.
        Specified by:
        first in interface PriorityQueue
        Returns:
        the first element.
      • last

        public java.lang.Object 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
        Returns:
        the last element.
      • changed

        public void changed()
        Description copied from interface: PriorityQueue
        Notifies the queue that the first element has changed (optional operation).

        This default implementation just throws an UnsupportedOperationException.

        Specified by:
        changed in interface PriorityQueue
      • comparator

        public java.util.Comparator<?> comparator()
        Description copied from interface: PriorityQueue
        Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
        Specified by:
        comparator in interface PriorityQueue
        Returns:
        the comparator associated with this sorted set, or null if it uses its elements' natural ordering.
      • clone

        public java.lang.Object clone()
      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.Object
      • equals

        public boolean equals​(java.lang.Object o)
        Overrides:
        equals in class java.lang.Object