Class AbstractQueue<E>

java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractQueue<E>
Type Parameters:
E - the type of the element in the collection.
All Implemented Interfaces:
Iterable<E>, Collection<E>, Queue<E>
Direct Known Subclasses:
PriorityQueue
public abstract class AbstractQueue<E> extends AbstractCollection<E> implements Queue<E>
AbstractQueue is an abstract class which implements some of the methods in Queue. The provided implementations of add, remove and element are based on offer, poll, and peek except that they throw exceptions to indicate some error instead of returning true or false.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    AbstractQueue()
    Constructor to be used by subclasses.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(E o)
    Adds an element to the queue.
    boolean
    addAll(Collection<? extends E> c)
    Adds all the elements of a collection to the queue.
    void
    clear()
    Removes all elements of the queue, leaving it empty.
    E
    element()
    Returns but does not remove the element at the head of the queue.
    E
    remove()
    Removes the element at the head of the queue and returns it.

    Methods inherited from class AbstractCollection

    contains, containsAll, isEmpty, iterator, remove, removeAll, retainAll, size, toArray, toArray, toString
    Modifier and Type
    Method
    Description
    boolean
    contains(Object object)
    Tests whether this Collection contains the specified object.
    boolean
    containsAll(Collection<?> collection)
    Tests whether this Collection contains all objects contained in the specified Collection.
    boolean
    isEmpty()
    Returns if this Collection contains no elements.
    abstract Iterator<E>
    iterator()
    Returns an instance of Iterator that may be used to access the objects contained by this Collection.
    boolean
    remove(Object object)
    Removes one instance of the specified object from this Collection if one is contained (optional).
    boolean
    removeAll(Collection<?> collection)
    Removes all occurrences in this Collection of each object in the specified Collection (optional).
    boolean
    retainAll(Collection<?> collection)
    Removes all objects from this Collection that are not also found in the Collection passed (optional).
    abstract int
    size()
    Returns a count of how many objects this Collection contains.
    Object[]
    toArray()
    Returns a new array containing all elements contained in this ArrayList.
    <T> T[]
    toArray(T[] contents)
    Returns an array containing all elements contained in this ArrayList.
    String
    toString()
    Returns the string representation of this Collection.

    Methods inherited from class Object

    clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
    Modifier and Type
    Method
    Description
    protected Object
    clone()
     
    boolean
    equals(Object obj)
    Indicates whether some other object is "equal to" this one.
    final Class
    getClass()
    Returns the runtime class of an object.
    int
    hashCode()
    Returns a hash code value for the object.
    final void
    notify()
    Wakes up a single thread that is waiting on this object's monitor.
    final void
    notifyAll()
    Wakes up all threads that are waiting on this object's monitor.
    final void
    wait()
    Causes current thread to wait until another thread invokes the method or the method for this object.
    final void
    wait(long timeout)
    Causes current thread to wait until either another thread invokes the method or the method for this object, or a specified amount of time has elapsed.
    final void
    wait(long timeout, int nanos)
    Causes current thread to wait until another thread invokes the method or the method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.

    Methods inherited from interface Collection

    equals, hashCode
    Modifier and Type
    Method
    Description
    boolean
    equals(Object object)
    Compares the argument to the receiver, and returns true if they represent the same object using a class specific comparison.
    int
    hashCode()
    Returns an integer hash code for the receiver.

    Methods inherited from interface Queue

    offer, peek, poll
    Modifier and Type
    Method
    Description
    boolean
    offer(E o)
    Inserts the specified element into the queue provided that the condition allows such an operation.
    E
    peek()
    Gets but does not remove the element at the head of the queue.
    E
    poll()
    Gets and removes the element at the head of the queue, or returns null if there is no element in the queue.

  • Constructor Details

    • AbstractQueue

      protected AbstractQueue()
      Constructor to be used by subclasses.

  • Method Details

    • add

      public boolean add(E o)
      Adds an element to the queue.
      Specified by:
      add in interface Collection<E>
      Overrides:
      add in class AbstractCollection<E>
      Parameters:
      o - the element to be added to the queue.
      Returns:
      true if the operation succeeds, otherwise false.
      Throws:
      IllegalStateException - if the element is not allowed to be added to the queue.

    • addAll

      public boolean addAll(Collection<? extends E> c)
      Adds all the elements of a collection to the queue. If the collection is the queue itself, then an IllegalArgumentException will be thrown. If during the process, some runtime exception is thrown, then those elements in the collection which have already successfully been added will remain in the queue. The result of the method is undefined if the collection is modified during the process of the method.
      Specified by:
      addAll in interface Collection<E>
      Overrides:
      addAll in class AbstractCollection<E>
      Parameters:
      c - the collection to be added to the queue.
      Returns:
      true if the operation succeeds, otherwise false.
      Throws:
      NullPointerException - if the collection or any element of it is null.
      IllegalArgumentException - If the collection to be added to the queue is the queue itself.

    • remove

      public E remove()
      Removes the element at the head of the queue and returns it.
      Specified by:
      remove in interface Queue<E>
      Returns:
      the element at the head of the queue.
      Throws:
      NoSuchElementException - if the queue is empty.

    • element

      public E element()
      Returns but does not remove the element at the head of the queue.
      Specified by:
      element in interface Queue<E>
      Returns:
      the element at the head of the queue.
      Throws:
      NoSuchElementException - if the queue is empty.

    • clear

      public void clear()
      Removes all elements of the queue, leaving it empty.
      Specified by:
      clear in interface Collection<E>
      Overrides:
      clear in class AbstractCollection<E>
      See Also: