RFR : 8016446 : (m) Add override forEach/replaceAll to HashMap, Hashtable, IdentityHashMap, WeakHashMap, TreeMap
Mike Duigou
mike.duigou at oracle.com
Tue Jun 18 23:16:27 UTC 2013
On Jun 18 2013, at 11:54 , Remi Forax wrote:
> 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();
> }
> }
> }
Corrected in the pushed version.
>
> Also there is no curly brace around "throw new CME();"
Also corrected in the pushed version.
>
> And I have an open question, in ConcurrentMap, the code use entrySet() but could use forEach,
> I wonder which one is better here ?
Good suggestion. I opted for the forEach. A capturing BiConsumer lambda is cheaper than the iterator overhead.
Thanks for your patient and thorough feedback on this issue.
Mike
> 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;
>>>>>>
>>>>>> /**
>>>>>> * <p>Hash table and linked list implementation of the <tt>Map</tt> 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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