--- jsr166/src/main/java/util/PriorityQueue.java	2003/08/06 01:57:53	1.23
+++ jsr166/src/main/java/util/PriorityQueue.java	2003/08/27 10:27:07	1.35
@@ -28,6 +28,18 @@
  * elements are added to a priority queue, its capacity grows
  * automatically.  The details of the growth policy are not specified.
  *
+ * <p>The Iterator provided in method {@link #iterator()} is <em>not</em>
+ * guaranteed to traverse the elements of the PriorityQueue in any
+ * particular order. If you need ordered traversal, consider using
+ * <tt>Arrays.sort(pq.toArray())</tt>.
+ *
+ * <p> <strong>Note that this implementation is not synchronized.</strong>
+ * Multiple threads should not access a <tt>PriorityQueue</tt>
+ * instance concurrently if any of the threads modifies the list
+ * structurally. Instead, use the thread-safe {@link
+ * java.util.concurrent.PriorityBlockingQueue} class.
+ *
+ * 
  * <p>Implementation note: this implementation provides O(log(n)) time
  * for the insertion methods (<tt>offer</tt>, <tt>poll</tt>,
  * <tt>remove()</tt> and <tt>add</tt>) methods; linear time for the
@@ -44,6 +56,8 @@
 public class PriorityQueue<E> extends AbstractQueue<E>
     implements Queue<E>, java.io.Serializable {
 
+    private static final long serialVersionUID = -7720805057305804111L;
+
     private static final int DEFAULT_INITIAL_CAPACITY = 11;
 
     /**
@@ -81,7 +95,7 @@ public class PriorityQueue<E> extends Ab
     /**
      * Creates a <tt>PriorityQueue</tt> with the default initial capacity
      * (11) that orders its elements according to their natural
-     * ordering (using <tt>Comparable</tt>.)
+     * ordering (using <tt>Comparable</tt>).
      */
     public PriorityQueue() {
         this(DEFAULT_INITIAL_CAPACITY, null);
@@ -90,7 +104,7 @@ public class PriorityQueue<E> extends Ab
     /**
      * Creates a <tt>PriorityQueue</tt> with the specified initial capacity
      * that orders its elements according to their natural ordering
-     * (using <tt>Comparable</tt>.)
+     * (using <tt>Comparable</tt>).
      *
      * @param initialCapacity the initial capacity for this priority queue.
      * @throws IllegalArgumentException if <tt>initialCapacity</tt> is less
@@ -159,7 +173,7 @@ public class PriorityQueue<E> extends Ab
      * specified collection.  The priority queue has an initial
      * capacity of 110% of the size of the specified collection or 1
      * if the collection is empty.  If the specified collection is an
-     * instance of a {@link SortedSet} or is another
+     * instance of a {@link java.util.SortedSet} or is another
      * <tt>PriorityQueue</tt>, the priority queue will be sorted
      * according to the same comparator, or according to its elements'
      * natural order if the collection is sorted according to its
@@ -176,17 +190,16 @@ public class PriorityQueue<E> extends Ab
      */
     public PriorityQueue(Collection<? extends E> c) {
         initializeArray(c);
-        if (c instanceof SortedSet<? extends E>) {
-            SortedSet<? extends E> s = (SortedSet<? extends E>) c;
+        if (c instanceof SortedSet) {
+            // @fixme double-cast workaround for compiler
+            SortedSet<? extends E> s = (SortedSet<? extends E>) (SortedSet)c;
             comparator = (Comparator<? super E>)s.comparator();
             fillFromSorted(s);
-        }
-        else if (c instanceof PriorityQueue<? extends E>) {
+        } else if (c instanceof PriorityQueue) {
             PriorityQueue<? extends E> s = (PriorityQueue<? extends E>) c;
             comparator = (Comparator<? super E>)s.comparator();
             fillFromSorted(s);
-        }
-        else {
+        } else {
             comparator = null;
             fillFromUnsorted(c);
         }
@@ -379,6 +392,7 @@ public class PriorityQueue<E> extends Ab
     }
 
     private class Itr implements Iterator<E> {
+
         /**
          * Index (into queue array) of element to be returned by
          * subsequent call to next.
@@ -399,15 +413,20 @@ public class PriorityQueue<E> extends Ab
          */
         private int expectedModCount = modCount;
 
+        // Workarounds until version that better handles remove() installed.
+        // These are used to copy-on-write the array upon first remove
+        private Object[] q = queue;
+        private int qsize = size;
+
         public boolean hasNext() {
-            return cursor <= size;
+            return cursor <= qsize;
         }
 
         public E next() {
             checkForComodification();
-            if (cursor > size)
+            if (cursor > qsize)
                 throw new NoSuchElementException();
-            E result = (E) queue[cursor];
+            E result = (E) q[cursor];
             lastRet = cursor++;
             return result;
         }
@@ -417,9 +436,13 @@ public class PriorityQueue<E> extends Ab
                 throw new IllegalStateException();
             checkForComodification();
 
-            PriorityQueue.this.remove(lastRet);
-            if (lastRet < cursor)
-                cursor--;
+            // Copy on first remove
+            if (q == queue) {
+                q = new Object[queue.length];
+                System.arraycopy(queue, 0, q, 0, queue.length);
+            }
+            PriorityQueue.this.remove(q[lastRet]);
+
             lastRet = 0;
             expectedModCount = modCount;
         }
@@ -451,8 +474,6 @@ public class PriorityQueue<E> extends Ab
      * Removes and returns the ith element from queue.  Recall
      * that queue is one-based, so 1 <= i <= size.
      *
-     * XXX: Could further special-case i==size, but is it worth it?
-     * XXX: Could special-case i==0, but is it worth it?
      */
     private E remove(int i) {
         assert i <= size;
@@ -461,8 +482,11 @@ public class PriorityQueue<E> extends Ab
         E result = (E) queue[i];
         queue[i] = queue[size];
         queue[size--] = null;  // Drop extra ref to prevent memory leak
-        if (i <= size)
+        if (i <= size) {
             fixDown(i);
+            fixUp(i);
+        }
+
         return result;
     }
 
@@ -486,7 +510,7 @@ public class PriorityQueue<E> extends Ab
             }
         } else {
             while (k > 1) {
-                int j = k >> 1;
+                int j = k >>> 1;
                 if (comparator.compare((E)queue[j], (E)queue[k]) <= 0)
                     break;
                 Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
@@ -507,17 +531,20 @@ public class PriorityQueue<E> extends Ab
     private void fixDown(int k) {
         int j;
         if (comparator == null) {
-            while ((j = k << 1) <= size) {
-                if (j<size && ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
+            while ((j = k << 1) <= size && (j > 0)) {
+                if (j<size && 
+                    ((Comparable<E>)queue[j]).compareTo((E)queue[j+1]) > 0)
                     j++; // j indexes smallest kid
+
                 if (((Comparable<E>)queue[k]).compareTo((E)queue[j]) <= 0)
                     break;
                 Object tmp = queue[j];  queue[j] = queue[k]; queue[k] = tmp;
                 k = j;
             }
         } else {
-            while ((j = k << 1) <= size) {
-                if (j < size && comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
+            while ((j = k << 1) <= size && (j > 0)) {
+                if (j<size && 
+                    comparator.compare((E)queue[j], (E)queue[j+1]) > 0)
                     j++; // j indexes smallest kid
                 if (comparator.compare((E)queue[k], (E)queue[j]) <= 0)
                     break;
@@ -525,13 +552,14 @@ public class PriorityQueue<E> extends Ab
                 k = j;
             }
         }
+
     }
 
 
     /**
      * Returns the comparator used to order this collection, or <tt>null</tt>
      * if this collection is sorted according to its elements natural ordering
-     * (using <tt>Comparable</tt>.)
+     * (using <tt>Comparable</tt>).
      *
      * @return the comparator used to order this collection, or <tt>null</tt>
      * if this collection is sorted according to its elements natural ordering.