--- jsr166/src/main/java/util/ArrayList.java	2016/11/30 03:31:47	1.45
+++ jsr166/src/main/java/util/ArrayList.java	2016/12/08 05:02:32	1.48
@@ -578,8 +578,9 @@ public class ArrayList<E> extends Abstra
      */
     public void clear() {
         modCount++;
-        Arrays.fill(elementData, 0, size, null);
-        size = 0;
+        final Object[] es = elementData;
+        for (int to = size, i = size = 0; i < to; i++)
+            es[i] = null;
     }
 
     /**
@@ -669,13 +670,17 @@ public class ArrayList<E> extends Abstra
                     outOfBoundsMsg(fromIndex, toIndex));
         }
         modCount++;
-        final Object[] es = elementData;
-        final int oldSize = size;
-        System.arraycopy(es, toIndex, es, fromIndex, oldSize - toIndex);
-        Arrays.fill(es, size -= (toIndex - fromIndex), oldSize, null);
+        shiftTailOverGap(elementData, fromIndex, toIndex);
         // checkInvariants();
     }
 
+    /** Erases the gap from lo to hi, by sliding down following elements. */
+    private void shiftTailOverGap(Object[] es, int lo, int hi) {
+        System.arraycopy(es, hi, es, lo, size - hi);
+        for (int to = size, i = (size -= hi - lo); i < to; i++)
+            es[i] = null;
+    }
+
     /**
      * A version of rangeCheck used by add and addAll.
      */
@@ -761,10 +766,8 @@ public class ArrayList<E> extends Abstra
                 w += end - r;
                 throw ex;
             } finally {
-                final int oldSize = size, deleted = end - w;
-                modCount += deleted;
-                System.arraycopy(es, end, es, w, oldSize - end);
-                Arrays.fill(es, size -= deleted, oldSize, null);
+                modCount += end - w;
+                shiftTailOverGap(es, w, end);
             }
         }
         // checkInvariants();
@@ -772,15 +775,17 @@ public class ArrayList<E> extends Abstra
     }
 
     /**
-     * Save the state of the {@code ArrayList} instance to a stream (that
-     * is, serialize it).
+     * Saves the state of the {@code ArrayList} instance to a stream
+     * (that is, serializes it).
      *
+     * @param s the stream
+     * @throws java.io.IOException if an I/O error occurs
      * @serialData The length of the array backing the {@code ArrayList}
      *             instance is emitted (int), followed by all of its elements
      *             (each an {@code Object}) in the proper order.
      */
     private void writeObject(java.io.ObjectOutputStream s)
-        throws java.io.IOException{
+        throws java.io.IOException {
         // Write out element count, and any hidden stuff
         int expectedModCount = modCount;
         s.defaultWriteObject();
@@ -799,8 +804,12 @@ public class ArrayList<E> extends Abstra
     }
 
     /**
-     * Reconstitute the {@code ArrayList} instance from a stream (that is,
-     * deserialize it).
+     * Reconstitutes the {@code ArrayList} instance from a stream (that is,
+     * deserializes it).
+     * @param s the stream
+     * @throws ClassNotFoundException if the class of a serialized object
+     *         could not be found
+     * @throws java.io.IOException if an I/O error occurs
      */
     private void readObject(java.io.ObjectInputStream s)
         throws java.io.IOException, ClassNotFoundException {
@@ -1362,6 +1371,9 @@ public class ArrayList<E> extends Abstra
         }
     }
 
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     */
     @Override
     public void forEach(Consumer<? super E> action) {
         Objects.requireNonNull(action);
@@ -1513,6 +1525,9 @@ public class ArrayList<E> extends Abstra
         return (bits[i >> 6] & (1L << i)) == 0;
     }
 
+    /**
+     * @throws NullPointerException {@inheritDoc}
+     */
     @Override
     public boolean removeIf(Predicate<? super E> filter) {
         return removeIf(filter, 0, size);
@@ -1547,9 +1562,7 @@ public class ArrayList<E> extends Abstra
             for (i = beg; i < end; i++)
                 if (isClear(deathRow, i - beg))
                     es[w++] = es[i];
-            final int oldSize = size;
-            System.arraycopy(es, end, es, w, oldSize - end);
-            Arrays.fill(es, size -= (end - w), oldSize, null);
+            shiftTailOverGap(es, w, end);
             // checkInvariants();
             return true;
         } else {