Circular reasoning Java lambda grouping

I am familiar with Lambdas and confused with the error I made in this line of code:

HashMap<Date,ArrayList<Trade>> groupTrades = allTrades.stream().collect(Collectors.groupingBy(Trade::getTradeDate()));

IntelliJ does not compile for loop inference

Solution

After a lot of pain, I have completed all this. I hope it is also useful to others

You can't use HashMap or ArrayList - as long as you use the interface map and list, the code should be:

Map<Date,List<Trade>> groupTrades = allTrades.stream().collect(Collectors.groupingBy(Trade::getTradeDate));

Please note that when any parameter in groupby does not match the expectation in the declaration of map, it may lead to a fairly general message