A Queue implementation that extends this class must - * minimally define a method {@link Queue#offer} which does not permit - * insertion of null elements, along with methods {@link - * Queue#peek}, {@link Queue#poll}, {@link Collection#size}, and - * {@link Collection#iterator}. Typically, additional methods will be - * overridden as well. If these requirements cannot be met, consider - * instead subclassing {@link AbstractCollection}. - * - *
This class is a member of the
- *
- * Java Collections Framework.
- *
- * @since 1.5
- * @author Doug Lea
- * @param This implementation returns true if offer succeeds,
- * else throws an IllegalStateException.
- *
- * @param e the element to add
- * @return true (as specified by {@link Collection#add})
- * @throws IllegalStateException if the element cannot be added at this
- * time due to capacity restrictions
- * @throws ClassCastException if the class of the specified element
- * prevents it from being added to this queue
- * @throws NullPointerException if the specified element is null and
- * this queue does not permit null elements
- * @throws IllegalArgumentException if some property of this element
- * prevents it from being added to this queue
- */
- public boolean add(E e) {
- if (offer(e))
- return true;
- else
- throw new IllegalStateException("Queue full");
- }
-
- /**
- * Retrieves and removes the head of this queue. This method differs
- * from {@link #poll 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.
- *
- * @return the head of this queue
- * @throws NoSuchElementException if this queue is empty
- */
- public E remove() {
- E x = poll();
- if (x != null)
- return x;
- else
- throw new NoSuchElementException();
- }
-
- /**
- * Retrieves, but does not remove, the head of this queue. This method
- * differs from {@link #peek 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.
- *
- * @return the head of this queue
- * @throws NoSuchElementException if this queue is empty
- */
- public E element() {
- E x = peek();
- if (x != null)
- return x;
- else
- throw new NoSuchElementException();
- }
-
- /**
- * Removes all of the elements from this queue.
- * The queue will be empty after this call returns.
- *
- * This implementation repeatedly invokes {@link #poll poll} until it
- * returns null.
- */
- public void clear() {
- while (poll() != null)
- ;
- }
-
- /**
- * 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.
- *
- * @param c collection containing elements to be added to this queue
- * @return 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
- * @throws NullPointerException if the specified collection contains a
- * null element and this queue does not permit null elements,
- * or if the specified collection is null
- * @throws 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
- * @throws IllegalStateException if not all the elements can be added at
- * this time due to insertion restrictions
- * @see #add(Object)
- */
- public boolean addAll(Collection c) {
- if (c == null)
- throw new NullPointerException();
- if (c == this)
- throw new IllegalArgumentException();
- boolean modified = false;
- for (E e : c)
- if (add(e))
- modified = true;
- return modified;
- }
-
-}