GS Collections Kata w/ JCF Solutions

[Brian Goetz]

Try compiling with -XDuseGraphInference.

On Jan 16, 2013, at 4:15 PM, Raab, Donald wrote:

> Great suggestion.  I just gave it a try.  Max takes a comparator and returns Optional so you have to add a call to get().  I was able to change the example to the following:
> 
> Map<Double, Collection<Customer>> multimap = this.company.getCustomers()
>    .stream()
>    .collect(Collectors.<Customer, Double>groupBy((Customer customer) ->
>        customer.getOrders()
>            .stream()
>            .explode((Stream.Downstream<LineItem> downstream, Order order) -> {
>                downstream.send(order.getLineItems());
>            })
>            .map(LineItem::getValue)
>            .max(Comparators.naturalOrder())
>            .get()));
> 
> I get an unchecked error on Comparators.naturalOrder() in IntelliJ, but adding <Double> there makes it ugly.
> 
> This is the GS Collections version of the kata, which also used max(), but calls this method on a DoubleIterable:
> 
> MutableListMultimap<Double, Customer> multimap = this.company.getCustomers()
>    .groupBy(customer -> customer.getOrders()
>        .asLazy()
>        .flatCollect(Order::getLineItems)
>        .collectDouble(LineItem::getValue)
>        .max());
> 
> Unfortunately, the type inference seems to be very successful at thwarting me trying to simplify the above example using the stream library features.  I would like to simplify down to this but can't seem to get it to work:
> 
> Map<Double, Collection<Customer>> multimap = this.company.getCustomers()
>    .stream()
>    .collect(groupBy((customer) ->
>        customer.getOrders()
>            .stream()
>            .explode((downstream, order) -> {
>                downstream.send(order.getLineItems());
>            })
>            .map(LineItem::getValue)
>            .max(Comparators.naturalOrder())
>            .get()));
> 
> 
> From: Joe Bowbeer [mailto:joe.bowbeer at gmail.com] 
> Sent: Wednesday, January 16, 2013 4:21 PM
> To: Raab, Donald [Tech]
> Cc: lambda-libs-spec-experts at openjdk.java.net; Motlin, Craig P. [Tech]; Weir, John [Tech]
> Subject: Re: GS Collections Kata w/ JCF Solutions
> 
> Thanks.
> 
> 
> Would it be better to rewrite the following using Stream.max()?
> 
> 
> .reduce(0.0, (x, y) -> Math.max(x, y))
> 
> --Joe
> 
>