--- jsr166/src/main/java/util/ArrayDeque.java	2005/09/16 23:59:27	1.22
+++ jsr166/src/main/java/util/ArrayDeque.java	2008/05/18 23:47:55	1.30
@@ -4,7 +4,6 @@
  */
 
 package java.util;
-import java.util.*; // for javadoc (till 6280605 is fixed)
 import java.io.*;
 
 /**
@@ -45,7 +44,7 @@ import java.io.*;
  * Iterator} interfaces.
  *
  * <p>This class is a member of the
- * <a href="{@docRoot}/../guide/collections/index.html">
+ * <a href="{@docRoot}/../technotes/guides/collections/index.html">
  * Java Collections Framework</a>.
  *
  * @author  Josh Bloch and Doug Lea
@@ -479,6 +478,14 @@ public class ArrayDeque<E> extends Abstr
         return removeFirst();
     }
 
+    private void checkInvariants() {
+        assert elements[tail] == null;
+        assert head == tail ? elements[head] == null :
+            (elements[head] != null &&
+             elements[(tail - 1) & (elements.length - 1)] != null);
+        assert elements[(head - 1) & (elements.length - 1)] == null;
+    }
+
     /**
      * Removes the element at the specified position in the elements array,
      * adjusting head and tail as necessary.  This can result in motion of
@@ -490,38 +497,42 @@ public class ArrayDeque<E> extends Abstr
      * @return true if elements moved backwards
      */
     private boolean delete(int i) {
-	int mask = elements.length - 1;
-	int front = (i - head) & mask;
-	int back  = (tail - i) & mask;
-
-	// Invariant: head <= i < tail mod circularity
-	if (front >= ((tail - head) & mask))
-	    throw new ConcurrentModificationException();
-
-	// Optimize for least element motion
-	if (front < back) {
-	    if (head <= i) {
-		System.arraycopy(elements, head, elements, head + 1, front);
-	    } else { // Wrap around
-		System.arraycopy(elements, 0, elements, 1, i);
-		elements[0] = elements[mask];
-		System.arraycopy(elements, head, elements, head + 1, mask - head);
-	    }
-	    elements[head] = null;
-	    head = (head + 1) & mask;
+        checkInvariants();
+        final E[] elements = this.elements;
+        final int mask = elements.length - 1;
+        final int h = head;
+        final int t = tail;
+        final int front = (i - h) & mask;
+        final int back  = (t - i) & mask;
+
+        // Invariant: head <= i < tail mod circularity
+        if (front >= ((t - h) & mask))
+            throw new ConcurrentModificationException();
+
+        // Optimize for least element motion
+        if (front < back) {
+            if (h <= i) {
+                System.arraycopy(elements, h, elements, h + 1, front);
+            } else { // Wrap around
+                System.arraycopy(elements, 0, elements, 1, i);
+                elements[0] = elements[mask];
+                System.arraycopy(elements, h, elements, h + 1, mask - h);
+            }
+            elements[h] = null;
+            head = (h + 1) & mask;
             return false;
-	} else {
-            int t = tail;
-            tail = (tail - 1) & mask;
-	    if (i < t) { // Copy the null tail as well
-		System.arraycopy(elements, i + 1, elements, i, back);
-	    } else {     // Wrap around
-		System.arraycopy(elements, i + 1, elements, i, mask - i);
-		elements[mask] = elements[0];
-		System.arraycopy(elements, 1, elements, 0, t);
-	    }
+        } else {
+            if (i < t) { // Copy the null tail as well
+                System.arraycopy(elements, i + 1, elements, i, back);
+                tail = t - 1;
+            } else { // Wrap around
+                System.arraycopy(elements, i + 1, elements, i, mask - i);
+                elements[mask] = elements[0];
+                System.arraycopy(elements, 1, elements, 0, t);
+                tail = (t - 1) & mask;
+            }
             return true;
-	}
+        }
     }
 
     // *** Collection Methods ***
@@ -583,12 +594,12 @@ public class ArrayDeque<E> extends Abstr
         }
 
         public E next() {
-            E result;
             if (cursor == fence)
                 throw new NoSuchElementException();
+            E result = elements[cursor];
             // This check doesn't catch all possible comodifications,
             // but does catch the ones that corrupt traversal
-            if (tail != fence || (result = elements[cursor]) == null)
+            if (tail != fence || result == null)
                 throw new ConcurrentModificationException();
             lastRet = cursor;
             cursor = (cursor + 1) & (elements.length - 1);
@@ -598,49 +609,47 @@ public class ArrayDeque<E> extends Abstr
         public void remove() {
             if (lastRet < 0)
                 throw new IllegalStateException();
-            if (delete(lastRet)) // if left-shifted, undo increment in next()
+            if (delete(lastRet)) { // if left-shifted, undo increment in next()
                 cursor = (cursor - 1) & (elements.length - 1);
+                fence = tail;
+            }
             lastRet = -1;
-            fence = tail;
         }
     }
 
-
     private class DescendingIterator implements Iterator<E> {
         /*
          * This class is nearly a mirror-image of DeqIterator, using
-         * (tail-1) instead of head for initial cursor, (head-1)
-         * instead of tail for fence, and elements.length instead of -1
-         * for sentinel. It shares the same structure, but not many
-         * actual lines of code.
+         * tail instead of head for initial cursor, and head instead of
+         * tail for fence.
          */
-        private int cursor = (tail - 1) & (elements.length - 1);
-        private int fence =  (head - 1) & (elements.length - 1);
-        private int lastRet = elements.length;
+        private int cursor = tail;
+        private int fence = head;
+        private int lastRet = -1;
 
         public boolean hasNext() {
             return cursor != fence;
         }
 
         public E next() {
-            E result;
             if (cursor == fence)
                 throw new NoSuchElementException();
-            if (((head - 1) & (elements.length - 1)) != fence ||
-                (result = elements[cursor]) == null)
+            cursor = (cursor - 1) & (elements.length - 1);
+            E result = elements[cursor];
+            if (head != fence || result == null)
                 throw new ConcurrentModificationException();
             lastRet = cursor;
-            cursor = (cursor - 1) & (elements.length - 1);
             return result;
         }
 
         public void remove() {
-            if (lastRet >= elements.length)
+            if (lastRet < 0)
                 throw new IllegalStateException();
-            if (!delete(lastRet))
+            if (!delete(lastRet)) {
                 cursor = (cursor + 1) & (elements.length - 1);
-            lastRet = elements.length;
-            fence = (head - 1) & (elements.length - 1);
+                fence = head;
+            }
+            lastRet = -1;
         }
     }
 
@@ -715,7 +724,7 @@ public class ArrayDeque<E> extends Abstr
      * @return an array containing all of the elements in this deque
      */
     public Object[] toArray() {
-	return copyElements(new Object[size()]);
+        return copyElements(new Object[size()]);
     }
 
     /**
@@ -760,7 +769,7 @@ public class ArrayDeque<E> extends Abstr
         if (a.length < size)
             a = (T[])java.lang.reflect.Array.newInstance(
                     a.getClass().getComponentType(), size);
-	copyElements(a);
+        copyElements(a);
         if (a.length > size)
             a[size] = null;
         return a;
@@ -776,9 +785,7 @@ public class ArrayDeque<E> extends Abstr
     public ArrayDeque<E> clone() {
         try {
             ArrayDeque<E> result = (ArrayDeque<E>) super.clone();
-            // These two lines are currently faster than cloning the array:
-            result.elements = (E[]) new Object[elements.length];
-            System.arraycopy(elements, 0, result.elements, 0, elements.length);
+            result.elements = Arrays.copyOf(elements, elements.length);
             return result;
 
         } catch (CloneNotSupportedException e) {
@@ -826,6 +833,5 @@ public class ArrayDeque<E> extends Abstr
         // Read in all elements in the proper order.
         for (int i = 0; i < size; i++)
             elements[i] = (E)s.readObject();
-
     }
 }