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 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: