如何建立Multi ConcurrentHashMap？

Question

guava library has useful MultuMap to replace Map<Object, Collection> to avoid null checks.

I cannot find analog MultiMap for ConcurrentHashMap .

Does it exist ?

Does Multimaps.forMap(new ConcurrentHashMap<Object, Object>()); correct?

PS

initialization:

private Multimap<Object, ComplexCalcStrategy> strategies = HashMultimap.<Object, ComplexCalcStrategy>create();

first thread:

for (Integer optionId : strategy.getOptions()) {
            strategies.put(optionId, strategy);
  }

second thread:

Collection<ComplexCalcStrategy> strategiesThatNeedUpdating = strategies.get(mktDataChange.getOptionId());
for (ComplexCalcStrategy strategy : strategiesThatNeedUpdating) { 
     updateMarketData(strategy.getStrategy(), mktDataChange);
}

Now this code leads to ConcurrentModificationexception .

Answer 1

If i remembar correctly HashMultimap.create(); and then ImmutableSetMultimap.Builder .

Answer 2

You could replace those sections with

initialization:

private final Map<Integer, Set<ComplexCalcStrategy>> strategies = new ConcurrentHashMap<>();

first thread:

for (Integer optionId : strategy.getOptions()) {
    strategies.computeIfAbsent(optionId, k -> Collections.newSetFromMap(new ConcurrentHashMap<>()))
              .add(strategy);
}

second thread:

for (ComplexCalcStrategy strategy : strategies.getOrDefault(optionId, Collections.emptySet())) { 
     updateMarketData(strategy.getStrategy(), mktDataChange);
}