--- jsr166/src/main/java/util/AbstractQueue.java 2003/08/04 01:50:33 1.11 +++ jsr166/src/main/java/util/AbstractQueue.java 2005/05/16 04:55:20 1.29 @@ -1,68 +1,86 @@ /* * Written by Doug Lea with assistance from members of JCP JSR-166 - * Expert Group and released to the public domain. Use, modify, and - * redistribute this code in any way without acknowledgement. + * Expert Group and released to the public domain, as explained at + * http://creativecommons.org/licenses/publicdomain */ package java.util; /** - * AbstractQueue provides default implementations of - * {@link #add add}, {@link #remove remove}, and {@link #element element} - * based on - * {@link #offer offer}, {@link #poll poll}, and {@link #peek peek}, - * respectively but that - * throw exceptions instead of indicating failure via false or + * This class provides skeletal implementations of some {@link Queue} + * operations. The implementations in this class are appropriate when + * the base implementation does not allow null + * elements. Methods {@link #add add}, {@link #remove remove}, and + * {@link #element element} are based on {@link #offer offer}, {@link + * #poll poll}, and {@link #peek peek}, respectively but throw + * exceptions instead of indicating failure via false or * null returns. - *
The provided implementations all assume that the base implementation - * does not allow null elements. + * + *
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 a + * {@link Collection#iterator} supporting {@link + * Iterator#remove}. 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.
*
- * @throws NullPointerException if the specified element is null
+ * @param e the element to add
+ * @return true (as per the spec for {@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 not permit null elements
+ * @throws IllegalArgumentException if some property of this element
+ * prevents it from being added to this queue
*/
- public boolean add(E o) {
- if (offer(o))
+ public boolean add(E e) {
+ if (offer(e))
return true;
else
throw new IllegalStateException("Queue full");
}
/**
- * Adds all of the elements in the specified collection to this queue.
- * The behavior of this operation is undefined if
- * the specified collection is modified while the operation is in
- * progress. (This implies that the behavior of this call is undefined if
- * the specified collection is this queue, and this queue is nonempty.)
- *
- * This implementation iterates over the specified collection, and adds
- * each object returned by the iterator to this collection, in turn.
+ * Retrieves and removes the head of this queue. This method differs
+ * from {@link #poll} only in that it throws an exception if this queue
+ * is empty.
*
- * @param c collection whose elements are to be added to this queue
- * @return true if this collection changed as a result of the
- * call.
- * @throws NullPointerException if c or any element in c
- * is null
- *
+ * 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 boolean addAll(Collection extends E> c) {
- return super.addAll(c);
- }
-
- /** @throws NoSuchElementException {@inheritDoc} */
public E remove() {
E x = poll();
if (x != null)
@@ -71,7 +89,17 @@ public abstract class AbstractQueue 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)
@@ -81,8 +109,9 @@ public abstract class AbstractQueue This implementation repeatedly invokes {@link #poll poll} until it
* returns null.
*/
@@ -91,11 +120,47 @@ public abstract class AbstractQueue 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 whose elements are 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 extends E> c) {
+ if (c == null)
+ throw new NullPointerException();
+ if (c == this)
+ throw new IllegalArgumentException();
+ boolean modified = false;
+ Iterator extends E> e = c.iterator();
+ while (e.hasNext()) {
+ if (add(e.next()))
+ modified = true;
+ }
+ return modified;
+ }
+}