Java 8 - how to get multiple attributes of an object from a List?

samba :

I have a list of locations returned by Google places API and decided to find a Place with a lowest price.

Here is how I implemented it with Java 8:

BigDecimal lowestPrice = places.stream()
                .collect(Collectors.groupingBy(Place::getPrice, Collectors.counting()))
                .entrySet().stream().min(Map.Entry.comparingByValue())
                .map(Map.Entry::getKey)
                .orElse(BigDecimal.ZERO); 

It returns me the lowest price but it'll be great to get a name of the Place as well (it has a name attribute).

How can I also return a name of the place with a lowest price?

Ousmane D. :

Firstly, it's really unclear what you want as at first, you seem to say that

I have a list of locations returned by Google places API and decided to find a Place with a lowest price.

then at the bottom of your description, you say that:

It returns me the lowest price but it'll be great to get a name of the Place as well (it has a name attribute).

as if the latter seems to be what you want?

Nevertheless, here are both solutions:

if you want to find the min value by the count after grouping for whatever reason that may be... then you could do something along the lines of:

 places.stream()
       .collect(Collectors.groupingBy(Place::getPrice))
       .entrySet().stream()
       .min(Comparator.comparingInt((Map.Entry<Integer, List<Place>> e) -> e.getValue().size()))
       .map(e -> new SimpleEntry<>(e.getKey(), e.get(0)));  

note that above i've used Integer as the entry key, feel free to change this to the appropriate type if it's not an Integer.

---

Otherwise, if you're simply after the object with the lowest price then you can do:

places.stream().min(Comparator.comparingInt(Place::getPrice));

or:

Collections.min(places, Comparator.comparingInt(Place::getPrice));

There's no need for grouping and all the stuff going on.