RFR : 8016446 : (m) Add override forEach/replaceAll to HashMap, Hashtable, IdentityHashMap, WeakHashMap, TreeMap (original) (raw)

Remi Forax forax at univ-mlv.fr
Tue Jun 18 18:54:37 UTC 2013

On 06/18/2013 01:30 AM, Mike Duigou wrote:

The webrev looks fine for me.

Nitpicking a little bit, in IdentityHashMap (forEach and replaceAll), t[index] is processed twice, by example in forEach, it would prefer this code:

 public void forEach(BiConsumer<? super K, ? super V> action) {
     Objects.requireNonNull(action);
     int expectedModCount = modCount;

     Object[] t = table;
     for (int index = 0; index < t.length; index += 2) {
         Object key = t[index];
         if (key != null) {
             action.accept((K) unmaskNull(key), (V) t[index + 1]);
         }

         if (modCount != expectedModCount)  {
             throw new ConcurrentModificationException();
         }
      }
 }

Also there is no curly brace around "throw new CME();"

And I have an open question, in ConcurrentMap, the code use entrySet() but could use forEach, I wonder which one is better here ?

cheers, Rémi

On Jun 17 2013, at 03:09 , Paul Sandoz wrote:

On Jun 14, 2013, at 11:57 PM, Mike Duigou <mike.duigou at oracle.com> wrote: I have updated the webrev again. In addition to moving the modification checks to be consistently after the operation for the most complete "fast-fail" behaviour I've also slightly enhanced the Map default to detect ISE thrown by setValue as a CME condition.

http://cr.openjdk.java.net/~mduigou/JDK-8016446/2/webrev/ There are some places where the indentation looks wonky e.g. HashMap & LinkedHashMap changes. I have restyled all of the diffs to make sure they are clean. The LinkedHashMap.forEach/replaceAll methods are checking modCount and throwing CME before the action is called. Corrected. The WeakHashMap.replaceAll method is checking the modCount per bucket, not-per element. Corrected. Are there existing tests for the overriding methods? I had believed so in Map/Defaults.java but replaceAll was absent. Now corrected in updated webrev http://cr.openjdk.java.net/~mduigou/JDK-8016446/3/webrev/ I had to add the improved default for ConcurrentMap which was present in the lambda repo in order to have correct behaviour. Since getOrDefault is already in ConcurrentMap I will include this but we have to be careful when we do a jsr 166 syncup to make sure that the defaults don't get lost. Mike Otherwise looks OK. Paul.

For interference detection the strategy I am advocating is : - serial non-stream operations (Collection.forEach/Iterator.forEachRemaining): per-element post-operation ("fast-fail", "best-efforts"). As Remi has pointed out the failure modes for collection.forEach() and for(:collection) will differ and it is a conscious choice to provide superior fast-fail than to match behaviour. - stream terminal operations, both serial and parallel : at completion if at all. Having the serial and parallel stream interference detection behaviours consistent is prioritized over making serial stream behaviour match behaviour of non-stream iteration methods. Mike On Jun 12 2013, at 22:28 , Mike Duigou wrote: I have updated my webrev with Remi's improvements and some other improvements to the fast-fail concurrent modification checking.

Revised webrev: http://cr.openjdk.java.net/~mduigou/JDK-8016446/1/webrev/ Mike

On Jun 12 2013, at 15:49 , Remi Forax wrote: On 06/12/2013 11:23 PM, Mike Duigou wrote: Hello all; This patch adds optimized implementations of Map.forEach and Map.replaceAll to HashMap, Hashtable, IdentityHashMap, WeakHashMap, TreeMap http://cr.openjdk.java.net/~mduigou/JDK-8016446/0/webrev/ The implementations traverse the map more efficiently than the default iterator implementation and sometimes avoid creation of transient Map.Entry instances. The fast-fail behaviour of the default implementation is retained. Mike Hi Mike, funnily I was writing HashMap.forEach/LinkedHashMap.forEach at the same time. (you need also to override forEach in LinkedHashMap because the one you inherits from HashMap doesn't use the linked list of entries). My code is slightly different from yours because I've moved the cases where the item is a red/black tree out of the fast path (the tree is created either if you are unlucky, if hashCode is badly written or if someone forge keys to have collisions) and does the modCount check for each element because a call to the consumer can change the underlying map so you can not do a modCount check only at the end. Rémi Here is the diff. diff -r 6df79b7bae6f src/share/classes/java/util/HashMap.java --- a/src/share/classes/java/util/HashMap.java Wed Jun 12 09:44:34 2013 +0100 +++ b/src/share/classes/java/util/HashMap.java Thu Jun 13 00:46:05 2013 +0200 @@ -28,6 +28,7 @@ import java.io.*; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; +import java.util.function.BiConsumer; import java.util.function.Consumer; import java.util.function.BiFunction; import java.util.function.Function; @@ -2615,6 +2616,54 @@ int capacity() { return table.length; } float loadFactor() { return loadFactor; } + + @Override + public void forEach(BiConsumer<? super K, ? super V> action) { + Objects.requireNonNull(action); + final int expectedModCount = modCount; + if (nullKeyEntry != null) { + forEachNullKey(expectedModCount, action); + } + Object[] table = this.table; + for(int index = 0; index < table.length; index++) {_ _+ Object item = table[index];_ _+ if (item == null) {_ _+ continue;_ _+ }_ _+ if (item instanceof HashMap.TreeBin) {_ _+ eachTreeNode(expectedModCount, ((TreeBin)item).first, action);_ _+ continue;_ _+ }_ _+ @SuppressWarnings("unchecked")_ _+ Entry<K,V> entry = (Entry<K,V>)item; + for (;entry != null; entry = (Entry<K,V>)entry.next) { + if (expectedModCount != modCount) { + throw new ConcurrentModificationException(); + } + action.accept(entry.key, entry.value); + } + } + } + + private void eachTreeNode(int expectedModCount, TreeNode<K,V> node, BiConsumer<? super K, ? super V> action) { + while (node != null) { + if (expectedModCount != modCount) { + throw new ConcurrentModificationException(); + } + @SuppressWarnings("unchecked") + Entry<K,V> entry = (Entry<K,V>)node.entry; + action.accept(entry.key, entry.value); + node = (TreeNode<K,V>)entry.next; + } + } + + private void forEachNullKey(int expectedModCount, BiConsumer<? super K, ? super V> action) { + if (expectedModCount != modCount) { + throw new ConcurrentModificationException(); + } + action.accept(null, nullKeyEntry.value); + } + /** * Standin until HM overhaul; based loosely on Weak and Identity HM. */ diff -r 6df79b7bae6f src/share/classes/java/util/LinkedHashMap.java --- a/src/share/classes/java/util/LinkedHashMap.java Wed Jun 12 09:44:34 2013 +0100 +++ b/src/share/classes/java/util/LinkedHashMap.java Thu Jun 13 00:46:05 2013 +0200 @@ -24,7 +24,8 @@ */ package java.util; -import java.io.*; + +import java.util.function.BiConsumer; /** *

Hash table and linked list implementation of the Map interface,

@@ -470,4 +471,16 @@ protected boolean removeEldestEntry(Map.Entry<K,V> eldest) { return false; } + + @Override + public void forEach(BiConsumer<? super K, ? super V> action) { + Objects.requireNonNull(action); + int expectedModCount = modCount; + for (Entry<K,V> entry = header.after; entry != header; entry = entry.after) { + if (expectedModCount != modCount) { + throw new ConcurrentModificationException(); + } + action.accept(entry.key, entry.value); + } + } }

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