RFR: jsr166 jdk integration 2018-05

[Paul Sandoz]

> On May 9, 2018, at 11:17 AM, Martin Buchholz <martinrb at google.com> wrote:
> 
> Time to do this, since Claes is also touching ArrayList.
> 
> http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/overview.html <http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/overview.html>
> 
> 8202685: Improve ArrayList replaceAll
> http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/replaceAll/index.html <http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/replaceAll/index.html>
> https://bugs.openjdk.java.net/browse/JDK-8202685 <https://bugs.openjdk.java.net/browse/JDK-8202685>
> 

ArrayList.java
—
      @Override
      public void replaceAll(UnaryOperator<E> operator) {
          Objects.requireNonNull(operator);
          final int expectedModCount = modCount;
          final Object[] es = elementData;
!         final int size = this.size;
!         for (int i = 0; modCount == expectedModCount && i < size; i++)
              es[i] = operator.apply(elementAt(es, i));
          if (modCount != expectedModCount)
              throw new ConcurrentModificationException();
-         modCount++;
      }

A CME is not necessarily associated with just structural modifications it could, on a best effort basis, be associated with any modification, which is cheaper to do for bulk operations rather than individual operations, and this operation can be used to perturb all the elements of the list (just like sort) causing strange and hard to track bugs while in the middle of iterating. IMHO its better to fail under such circumstances rather than be silent.


> 8201386: Miscellaneous changes imported from jsr166 CVS 2018-05
> http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/miscellaneous/index.html <http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/miscellaneous/index.html>
> https://bugs.openjdk.java.net/browse/JDK-8201386 <https://bugs.openjdk.java.net/browse/JDK-8201386>
> 



PriorityQueue
—

 587     public E poll() {
 588         final Object[] es;
 589         final E result;
 590 
 591         if ((result = (E) ((es = queue)[0])) != null) {
 592             modCount++;
 593             final int n;
 594             final E x = (E) es[(n = --size)];
 595             es[n] = null;
 596             if (n > 0) {
 597                 final Comparator<? super E> cmp;
 598                 if ((cmp = comparator) == null)
 599                     siftDownComparable(0, x, es, n);
 600                 else
 601                     siftDownUsingComparator(0, x, es, n, cmp);
 602             }
 603         }
 604         return result;
 605     }

Why inline the siftDown method?

Paul.