GeeCon 2016 - Beyond Lambdas, the Aftermath

Beyond Lambdas, the
aftermath
@DanielSawano
@DanielDeogun
Deogun - Sawano, 11-13 May 2016

About us…
Daniel Sawano, Daniel Deogun Kraków, 11-13 May 2016
Daniel Deogun Daniel Sawano
Stockholm - Gothenburg - Malmoe - Umea - New York

[inert code here]

Optionals 1
7 final Oracle oracle = new Oracle();
8
9 String _() {
10 final Advise advise = currentAdvise();
11
12 if (advise != null) {
13 return advise.cheap();
14 }
15 else {
16 return oracle.advise().expensive();
17 }
18 }

Optionals 1
26
27 String _() {
29
30 return Optional.ofNullable(advise)
31 .map(Advise::cheap)
32 .orElse(oracle.advise().expensive());
33 }

Optionals 1
26
27 String _() {
29
30 return Optional.ofNullable(advise)
31 .map(Advise::cheap)
32 .orElseGet( () -> oracle.advise().expensive());
33 }

Optionals 2
26 String _(final Optional<String> optOfSomeValue) {
27
28 return optOfSomeValue.map(v -> calculate(v))
29 .filter(someCriteria())
30 .map(v -> transform(v))
31 .orElseGet(() -> completelyDifferentCalculation());
32
33 }

Optionals 2
26 String _(final Optional<String> optOfSomeValue) {
27
28 if (optOfSomeValue.isPresent()) {
29 final String calculatedValue = calculate(optOfSomeValue.get());
30 if (someCriteria().test(calculatedValue)) {
31 return transform(calculatedValue);
32 }
33 }
34
35 return completelyDifferentCalculation();
36
37 }

Optionals 2
26 String _() {
27 return value()
28 .flatMap(v -> firstCalculation(v))
29 .orElseGet(() -> completelyDifferentCalculation());
30 }
31
32 Optional<String> value() {
33 return Optional.of(someValue());
34 }
35
36 Optional<String> firstCalculation(final String v) {
37 return Optional.of(calculate(v))
38 .filter(someCriteria())
39 .map(value -> transform(value));
40 }

Optionals 3
27 <T> void _(final Optional<T> argument) {
28 argument.map(a -> doSomething(a));
29 }

Optionals 3
25 <T> void _(final T argument) {
26 if (argument != null) {
27 doSomething(argument);
28 }
29 }

Optionals 3
26 <T> void _(final T argument) {
27 doSomething(notNull(argument));
28 }

Streams 1
30 @Test
31 public void _() {
32
33 final Stream<String> stream = elements().stream()
34 .sorted();
35
36 final String result = stream.collect(joining(","));
37
38 assertEquals("A,B,C", result);
39
40 }
41
42 static List<String> elements() {
43 return asList("C", "B", null, "A");
44 }

Streams 1
31 @Test
33
34 final Stream<String> stream = elements().stream()
35 .filter(Objects::nonNull)
36 .sorted();
37
38 final String result = stream.collect(joining(","));
39
40 assertEquals("A,B,C", result);
41
42 }
43
44 static List<String> elements() {
45 return asList("C", "B", null, "A");
46 }

Streams 2
27 @Test
29
30 final long idToFind = 6;
31 final Predicate<Item> idFilter = item -> item.id().equals(idToFind);
32
33 service().itemsMatching(idFilter)
34 .findFirst()
35 .ifPresent(Support::doSomething);
36
37 }

Streams 2
28 @Test
30
31 final long idToFind = 6;
32 final Predicate<Item> idFilter = item -> item.id().equals(idToFind);
33
34 service().itemsMatching(idFilter)
35 .reduce(toOneItem())
36 .ifPresent(Support::doSomething);
37
38 }
39
40 BinaryOperator<Item> toOneItem() {
41 return (item, item2) -> {
42 throw new IllegalStateException("Found more than one item with the same id");
43 };
44 }

Streams 3
29 private final UserService userService = new UserService();
30 private final OrderService orderService = new OrderService();
31
32 @Test
34 givenALoggedInUser(userService);
35
36 itemsToBuy().stream()
37 .map(item -> new Order(item.id(), currentUser().id()))
38 .forEach(orderService::sendOrder);
39
40 System.out.println(format("Sent %d orders", orderService.sentOrders()));
41 }
42
43 User currentUser() {
44 final User user = userService.currentUser();
45 validState(user != null, "No current user found");
46 return user;
47 }

Streams 3
29 private final UserService userService = new UserService();
30 private final OrderService orderService = new OrderService();
31
32 @Test
34 givenALoggedInUser(userService);
35
36 final User user = currentUser();
37 itemsToBuy().parallelStream()
38 .map(item -> new Order(item.id(), user.id()))
39 .forEach(orderService::sendOrder);
40
41 System.out.println(format("Sent %d orders", orderService.sentOrders()));
42 }
43
44 User currentUser() {
45 final User user = userService.currentUser();
46 validState(user != null, "No current user found");
47 return user;
48 }

LAmbdas 1
28 static Integer numberOfFreeApples(final User user,
29 final Function<User, Integer> foodRatio) {
30 return 2 * foodRatio.apply(user);
31 }
32
33 @Test
35
36 final Function<User, Integer> foodRatioForVisitors = u -> u.age() > 12 ? 2 : 1;
37
38 final int numberOfFreeApples = numberOfFreeApples(someUser(), foodRatioForVisitors);
39
40 System.out.println(format("Number of free apples: %d", numberOfFreeApples));
41
42 }

LAmbdas 1
29 @Test
31
32 final Function<User, Integer> foodRatioForVisitors = u -> u.age() > 12 ? 2 : 1;
33 final Function<User, Integer> age = User::age;
34
35 final int numberOfFreeApples_1 = numberOfFreeApples(someUser(), foodRatioForVisitors);
36 final int numberOfFreeApples_2 = numberOfFreeApples(someUser(), age); // This is a bug!
37
38 System.out.println(format("Number of free apples (1): %d", numberOfFreeApples_1));
40
41 }

LAmbdas 1
28 @FunctionalInterface
29 interface FoodRatioStrategy {
30
31 Integer ratioFor(User user);
32 }
33
34 static Integer numberOfFreeApples(final User user,
35 final FoodRatioStrategy ratioStrategy) {
36 return 2 * ratioStrategy.ratioFor(user);
37 }
38
39 @Test
41
42 final FoodRatioStrategy foodRatioForVisitors = user -> user.age() > 12 ? 2 : 1;
43 final Function<User, Integer> age = User::age;
44
45 final Integer numberOfFreeApples_1 = numberOfFreeApples(someUser(), foodRatioForVisitors);
46 //final Integer numberOfFreeApples_2 = numberOfFreeApples(someUser(), age);
47
49 }

LAmbdas 2
25 @Test
26 public void should_build_tesla() {
27
28 assertEquals(1000, new TeslaFactory().createTesla().engine().horsepower());
29
30 }
31
32 @Test
33 public void should_build_volvo() {
34
35 assertEquals(250, new VolvoFactory().createVolvo().engine().horsepower());
36
37 }

LAmbdas 3
29 @Test
31
32 final List<Integer> values = asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
33
34 allEvenNumbers(values);
35
36 System.out.println("Hello");
37
38 }
39
40 static List<Integer> allEvenNumbers(final List<Integer> values) {
41 return values.stream()
42 .filter(Support::isEven)
43 .collect(toList());
44 }

LAmbdas 3
31 @Test
33
34 final List<Integer> values = asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
35
36 final Supplier<List<Integer>> integers = () -> allEvenNumbers(values);
37
38 System.out.println(integers.get());
39
40 }
41
42 static List<Integer> allEvenNumbers(final List<Integer> values) {
43 return values.stream()
44 .filter(Support::isEven)
46 }

LAmbdas 4
24 private final String pattern;
25
26 public _14(final String pattern) {
27 this.pattern = pattern;
28 }
29
30 public List<String> allMatchingElements(final List<String> elements) {
31 return elements.stream()
32 .filter(e -> e.contains(pattern))
34 }

LAmbdas 4
25 private final String pattern;
26
27 public _14(final String pattern) {
28 this.pattern = pattern;
29 }
30
31 public List<String> allMatchingElements(final List<String> elements) {
32 return elements.stream()
33 .filter(matches(pattern))
35 }
36
37 private Predicate<String> matches(final String pattern) {
38 return e -> e.contains(pattern);
39 }

Q&A
[Questions]

Code examples can be found here:
https://github.com/sawano/beyond-lambdas-the-aftermath

Thank you!
@DanielSawano @DanielDeogun

GeeCon 2016 - Beyond Lambdas, the Aftermath

More Related Content

What's hot (18)

Viewers also liked (20)

Similar to GeeCon 2016 - Beyond Lambdas, the Aftermath (20)

More from Daniel Sawano (10)

Recently uploaded (20)

GeeCon 2016 - Beyond Lambdas, the Aftermath