Module java.base
Package java.util

Class AbstractQueue<E>

    • Constructor Detail

      • AbstractQueue

        protected AbstractQueue​()
        Constructor for use by subclasses.
    • Method Detail

      • add

        public boolean add​(E e)
        Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available.

        This implementation returns true if offer succeeds, else throws an IllegalStateException.

        Specified by:
        add in interface Collection<E>
        Specified by:
        add in interface Queue<E>
        Overrides:
        add in class AbstractCollection<E>
        Parameters:
        e - the element to add
        Returns:
        true (as specified by Collection.add(E))
        Throws:
        IllegalStateException - if the element cannot be added at this time due to capacity restrictions
        ClassCastException - if the class of the specified element prevents it from being added to this queue
        NullPointerException - if the specified element is null and this queue does not permit null elements
        IllegalArgumentException - if some property of this element prevents it from being added to this queue
      • remove

        public E remove​()
        Retrieves and removes the head of this queue. This method differs from poll only in that it throws an exception if this queue is empty.

        This implementation returns the result of poll unless the queue is empty.

        Specified by:
        remove in interface Queue<E>
        Returns:
        the head of this queue
        Throws:
        NoSuchElementException - if this queue is empty
      • element

        public E element​()
        Retrieves, but does not remove, the head of this queue. This method differs from peek only in that it throws an exception if this queue is empty.

        This implementation returns the result of peek unless the queue is empty.

        Specified by:
        element in interface Queue<E>
        Returns:
        the head of this queue
        Throws:
        NoSuchElementException - if this queue is empty
      • clear

        public void clear​()
        Removes all of the elements from this queue. The queue will be empty after this call returns.

        This implementation repeatedly invokes poll until it returns null.

        Specified by:
        clear in interface Collection<E>
        Overrides:
        clear in class AbstractCollection<E>
      • addAll

        public boolean addAll​(Collection<? extends E> c)
        Adds all of the elements in the specified collection to this queue. Attempts to addAll of a queue to itself result in IllegalArgumentException. Further, the behavior of this operation is undefined if the specified collection is modified while the operation is in progress.

        This implementation iterates over the specified collection, and adds each element returned by the iterator to this queue, in turn. A runtime exception encountered while trying to add an element (including, in particular, a null element) may result in only some of the elements having been successfully added when the associated exception is thrown.

        Specified by:
        addAll in interface Collection<E>
        Overrides:
        addAll in class AbstractCollection<E>
        Parameters:
        c - collection containing elements to be added to this queue
        Returns:
        true if this queue changed as a result of the call
        Throws:
        ClassCastException - if the class of an element of the specified collection prevents it from being added to this queue
        NullPointerException - if the specified collection contains a null element and this queue does not permit null elements, or if the specified collection is null
        IllegalArgumentException - if some property of an element of the specified collection prevents it from being added to this queue, or if the specified collection is this queue
        IllegalStateException - if not all the elements can be added at this time due to insertion restrictions
        See Also:
        add(Object)