--- jsr166/src/main/java/util/AbstractQueue.java	2003/08/04 01:50:33	1.11
+++ jsr166/src/main/java/util/AbstractQueue.java	2003/10/05 22:59:21	1.19
@@ -7,15 +7,24 @@
 package java.util;
 
 /**
- * <tt>AbstractQueue</tt> 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 <tt>false</tt> or
+ * This class provides skeletal implementations of some {@link Queue}
+ * operations. The implementations in this class are appropriate when
+ * the base implementation does <em>not</em> allow <tt>null</tt>
+ * 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 <tt>false</tt> or
  * <tt>null</tt> returns.
- * <p>The provided implementations all assume that the base implementation
- * does <em>not</em> allow <tt>null</tt> elements.
+ *
+ * <p> A <tt>Queue</tt> implementation that extends this class must
+ * minimally define a method {@link Queue#offer} which does not permit
+ * insertion of <tt>null</tt> 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}.
+ *
  * @since 1.5
  * @author Doug Lea
  */
@@ -23,16 +32,24 @@ public abstract class AbstractQueue<E>
     extends AbstractCollection<E>
     implements Queue<E> {
 
-    // note that optional methods are not optional here or in our subclasses,
-    // so we redefine each optional method to document that it is not optional
-    // We also inherit, or define, all necessary @throws comments
+    /**
+     * Constructor for use by subclasses.
+     */
+    protected AbstractQueue() {
+    }
+
 
     /**
-     * Adds the specified element to this queue.
+     * Adds the specified element to this queue. This implementation
+     * returns <tt>true</tt> if <tt>offer</tt> succeeds, else
+     * throws an IllegalStateException. 
+     * 
+     * @param o the element
      * @return <tt>true</tt> (as per the general contract of
-     * <tt>Collection.add</tt>).
+     *         <tt>Collection.add</tt>).
      *
      * @throws NullPointerException if the specified element is <tt>null</tt>
+     * @throws IllegalStateException if element cannot be added
      */
     public boolean add(E o) {
         if (offer(o))
@@ -42,27 +59,13 @@ public abstract class AbstractQueue<E>
     }
 
     /**
-     * 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.)
-     * <p>
-     * 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 implementation returns the result of <tt>poll</tt>
+     * unless the queue is empty.
      *
-     * @param c collection whose elements are to be added to this queue
-     * @return <tt>true</tt> if this collection changed as a result of the
-     *         call.
-     * @throws NullPointerException if <tt>c</tt> or any element in <tt>c</tt>
-     * is <tt>null</tt>
-     * 
+     * @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 +74,15 @@ public abstract class AbstractQueue<E>
             throw new NoSuchElementException();
     }
 
-    /** @throws NoSuchElementException {@inheritDoc} */
+
+    /**
+     * Retrieves, but does not remove, the head of this queue.  
+     * This implementation returns the result of <tt>peek</tt>
+     * 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)
@@ -91,11 +102,42 @@ public abstract class AbstractQueue<E>
             ;
     }
 
-    // XXX Remove this redundant declaration, pending response from Neal Gafter.
-    public abstract Iterator<E> iterator();
-}
-
-
-
-
+    /**
+     * Adds all of the elements in the specified collection to this
+     * queue.  Attempts to addAll of a queue to itself result in
+     * <tt>IllegalArgumentException</tt>. Further, the behavior of
+     * this operation is undefined if the specified collection is
+     * modified while the operation is in progress.
+     *
+     * <p>This implementation iterates over the specified collection,
+     * and adds each element returned by the iterator to this
+     * collection, in turn.  A runtime exception encountered while
+     * trying to add an element (including, in particular, a
+     * <tt>null</tt> 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 collection.
+     * @return <tt>true</tt> if this collection changed as a result of the
+     *         call.
+     * @throws NullPointerException if the specified collection, or
+     * any of its elements are null.
+     * @throws IllegalArgumentException if c is this queue.
+     * 
+     * @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;
+    }
 
+}