Java 8 code optimization - remove if statements

Question

I'm learning some tricks from Java 8. I created a simple list:

 private void createData() {
        bottles.add(new Whiskey("Jack Daniels", "PL"));
        bottles.add(new Whiskey("Balentains", "PL"));
        bottles.add(new Whiskey("Balentains", "EN"));
        bottles.add(new Whiskey("Balentains", "EN"));
        bottles.add(new Whiskey("Balentains", "GR"));
        bottles.add(new Whiskey("Balentains", "PL"));
        bottles.add(new Whiskey("Balentains", "GR"));
    }

And now I would like to get items from this list by few things. If user give a parameter origin, I want to filter this list by origins, but when he gave wrong origin then he should get empty list and when he won't give origin parameter then he should get whole list.

I have a method which filtering items in list:

 private Optional<List<Whiskey>> getWhiskeyFromCountry(String origin) {
        final List<Whiskey> whiskies = bottles.stream()
                .filter(b -> b.getOrigin().equals(origin))
                .collect(Collectors.toList());

        return whiskies.isEmpty() ? Optional.empty() : Optional.of(whiskies);
    }

And also a main method which get parameter (or not) and response with result:

private void getAll(RoutingContext routingContext) {
        Optional<String> origin = Optional.ofNullable(routingContext.request().params().get("filter"));
        List<Whiskey> result = getWhiskeyFromCountry(origin.orElse("")).orElse(Collections.EMPTY_LIST);

        routingContext.response()
                .putHeader("content-type", "application/json; charset=utf-8")
                .end(Json.encodePrettily(origin.isPresent() ? result : bottles));
    }

The problem is that I still use if statemant in last line and I do not want do this. I would like to change this code into clear and functional. I tried to do some magic with Optionals but in the end I got this one and I think it can be do better and simpler. Could you help me? Or maybe this code is good and I do not need to change anything? This question is more about clean code.

Just return a List from the getWhiskeyFromCountry method. If the origin is wrong, the list will be empty. — Alex R
– Alex R, Commented Oct 19, 2019 at 19:54
@AlexR - it is ok, but still I need to check if statement in last line — Developus
– Developus, Commented Oct 19, 2019 at 20:01
Why are you trying to avoid if statements? AN if statement is nice, clear, fast, and maintainable. Chains of functional code are not, and perform horribly. — Gabe Sechan
– Gabe Sechan, Commented Oct 19, 2019 at 20:01
@allocer No, if you're trying to use streams to minimize if statements, you're not understanding streams, funcitonal programming, and making less readable code. You're replacing a nice, easily readable high performing if with a slow, low performance, less readable function call. This is not something you should be attempting to do. It's poor style and bad programming. — Gabe Sechan
– Gabe Sechan, Commented Oct 19, 2019 at 23:46

Ryuzaki L · Accepted Answer · 2019-10-20 00:24:01Z

2

You can make this method getWhiskeyFromCountry to accept Optional<String> as parameter

private List<Whiskey> getWhiskeyFromCountry(Optional<String> origin)

and then if Optional is empty return empty list or return list based on filter, If user enters the wrong origin still you will get the empty list

return origin.map(o->bottles.stream()
            .filter(b -> b.getOrigin().equals(o))
            .collect(Collectors.toList())).orElse(Collections.EMPTY_LIST);

Or in the above code you can make small tweak to return List for this method getWhiskeyFromCountry

 private List<Whiskey> getWhiskeyFromCountry(String origin) {

    return bottles.stream()
            .filter(b -> b.getOrigin().equals(origin))
            .collect(Collectors.toList());
  }

And in the main method use Optional.map

Optional<String> origin = Optional.ofNullable(routingContext.request().params().get("filter"));
List<Whiskey> result = origin.map(o->getWhiskeyFromCountry(o))
                             .orElse(bottles);

edited Oct 20, 2019 at 0:24

answered Oct 19, 2019 at 19:55

Ryuzaki L

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5 Comments

Hadi Over a year ago

Passing Optional as parameter is not best practice!

Ryuzaki L Over a year ago

May i know why @HadiJ ?

Hadi Over a year ago

@Deadpool, Although I disagree by getting origin as optional, but for your second approach to avoid double checking i think it's better use this origin.map(o->getWhiskeyFromCountry(o)) .orElse(bottles);

Hadi Over a year ago

Or maybe something like this

Optional<String> getParam(RoutingContext routingContext){return Optional.ofNullable(routingContext.request().params().get("filter"));}

and then in getAll method getParam(routingContext).map(o->getWhiskeyFromCountry(o)) .orElse(bottles);

Naman Over a year ago

For references to what @HadiJ pointed out. Why should Optional not be used in arguments.

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