Cleaner code with Guava v2

Cleaner code with Guava - v2 presented at IO Extended in Madrid

Transcript

1. Cleaner code with Guava @alexsimonescu
2. http://bit.ly/204MhVV
3. Alexandru Simonescu http://blog.alexsimo.com http://alexsimo.com @alexsimonescu hi@alexsimo.com “Do what you love. Love what you do.” - Ray Bradbury
5. Our mission - Write cleaner code - Be more productive - Open mind to new workflows - Discover new types
6. What is Guava?
7. What is Guava? - Google’s core Java library - Utilities classes and methods - Used in Google and Netflix
8. Guava components hashing event bus math reflection networking annotations basic utilities collections concurrency comparison strings primitives ranges functional I/O cache
9. Guava components hashing event bus math reflection networking annotations basic utilities collections concurrency ordering strings primitives ranges functional I/O cache
10. Basic
11. We all love null
12. But what “null” really means?
13. Failure? Success? Absence?
14. Domain problems in Domain Driven Design
15. Null use cases - None - Represent some sort of absence - Value not found - Something went wrong :(
16. Your task 2. Find better alternative 1. Identify what really means enums constants builders
17. Optional
18. Optional - may contain non null value (reference is present) - may contain nothing (reference is absent)
19. Optional<String> name = Optional.of("Alex");
 Optional<Integer> age = Optional.absent();
 Optional<String> car = Optional.fromNullable(null);
 
 
 System.out.println(String.format("Name exists: %s", name.isPresent())); System.out.println(String.format("Age or default: %s", age.or(0))); 
 System.out.println(String.format("Car: %s", car.toString()));
20. Optional goodness - Increases readability - Makes you analyze absent case - Never forget if a value can be null - Forces you to unwrap Optional<T>
21. Strings
22. Strings goodness - Join and split strings easily - Characters matching helpers - Safe charsets
23. List<String> fruits = Arrays.asList(
 null, "banana", null, "blackberry", null, "guava");
 String joined = Joiner.on(", ").skipNulls().join(fruits);
 
 // banana, blackberry, guava String contacts = "alex:123;bob:321;ana:333;daniel:890;victor: 456";
 
 Splitter.MapSplitter mapSplitter = Splitter.on(";").withKeyValueSeparator(":");
 Map<String, String> descompose = mapSplitter.split(contacts);
 for (Map.Entry<String, String> f : descompose.entrySet()) {
 println(String.format("%s -> %s", f.getKey(), f.getValue()));
 } // alex -> 123 // bob -> 321 // ana -> 333
24. Person person = persons.get(ONE);
 StringBuffer sb = new StringBuffer();
 sb.append(person.getSuffix());
 sb.append(" --- ");
 sb.append(person.getName());
 sb.append(" --- ");
 sb.append(person.getPhoneNumber());
 String phone = CharMatcher.DIGIT.retainFrom(sb);

25. Objects
26. Objects goodness - Easy toString(), hashCode() and equals() - Cleaner compareTo() - Objects comparator
27. @Override
 public boolean equals(Object o) {
 if (this == o) return true;
 if (o == null || getClass() != o.getClass()) return false;
 
 Person person = (Person) o;
 
 if (firstName != null ? !firstName.equals(person.firstName) : person.firstName != null) return false;
 if (lastName != null ? !lastName.equals(person.lastName) : person.lastName != null) return false;
 if (name != null ? !name.equals(person.name) : person.name != null) return false;
 if (suffix != null ? !suffix.equals(person.suffix) : person.suffix != null) return false;
 if (phoneNumber != null ? !phoneNumber.equals(person.phoneNumber) : person.phoneNumber != null) return false;
 if (email != null ? !email.equals(person.email) : person.email != null) return false;
 if (website != null ? !website.equals(person.website) : person.website != null) return false;
 if (address != null ? !address.equals(person.address) : person.address != null) return false;
 return car != null ? car.equals(person.car) : person.car == null;
 
 }
 
 @Override
 public int hashCode() {
 int result = firstName != null ? firstName.hashCode() : 0;
 result = 31 * result + (lastName != null ? lastName.hashCode() : 0);
 result = 31 * result + (name != null ? name.hashCode() : 0);
 result = 31 * result + (suffix != null ? suffix.hashCode() : 0);
 result = 31 * result + (phoneNumber != null ? phoneNumber.hashCode() : 0);
 result = 31 * result + (email != null ? email.hashCode() : 0);
 result = 31 * result + (website != null ? website.hashCode() : 0);
 result = 31 * result + (address != null ? address.hashCode() : 0);
 result = 31 * result + (car != null ? car.hashCode() : 0);
 return result;
 }
29. @Override
 public boolean equals(Object o) {
 if (this == o) return true;
 if (o == null || getClass() != o.getClass()) return false;
 
 Person person = (Person) o;
 
 if (firstName != null ? !firstName.equals(person.firstName) : person.firstName != null) return false;
 if (lastName != null ? !lastName.equals(person.lastName) : person.lastName != null) return false;
 if (name != null ? !name.equals(person.name) : person.name != null) return false;
 if (suffix != null ? !suffix.equals(person.suffix) : person.suffix != null) return false;
 if (phoneNumber != null ? !phoneNumber.equals(person.phoneNumber) : person.phoneNumber != null) return false;
 if (email != null ? !email.equals(person.email) : person.email != null) return false;
 if (website != null ? !website.equals(person.website) : person.website != null) return false;
 if (address != null ? !address.equals(person.address) : person.address != null) return false;
 return car != null ? car.equals(person.car) : person.car == null;
 
 }
 
 @Override
 public int hashCode() {
 int result = firstName != null ? firstName.hashCode() : 0;
 result = 31 * result + (lastName != null ? lastName.hashCode() : 0);
 result = 31 * result + (name != null ? name.hashCode() : 0);
 result = 31 * result + (suffix != null ? suffix.hashCode() : 0);
 result = 31 * result + (phoneNumber != null ? phoneNumber.hashCode() : 0);
 result = 31 * result + (email != null ? email.hashCode() : 0);
 result = 31 * result + (website != null ? website.hashCode() : 0);
 result = 31 * result + (address != null ? address.hashCode() : 0);
 result = 31 * result + (car != null ? car.hashCode() : 0);
 return result;
 }
30. @Override
 public String toString() {
 return MoreObjects.toStringHelper(this)
 .add("firstName", firstName)
 .add("lastName", lastName)
 .add("name", name)
 .add("suffix", suffix)
 .add("phoneNumber", phoneNumber)
 .add("email", email)
 .add("website", website)
 .add("address", address.toString())
 .toString();
 }
31. @Override
 public boolean equals(Object object) {
 
 if (object instanceof Person) {
 Person that = (Person) object;
 return Objects.equal(this.name, that.name)
 && Objects.equal(this.firstName, that.firstName)
 && Objects.equal(this.email, that.email);
 }
 return false;
 }
 
 @Override
 public int hashCode() {
 return Objects.hashCode(name, firstName, email);
 }
32. @Override
 public int compareTo(Person o) {
 return ComparisonChain.start()
 .compare(this.name, o.name)
 .compare(this.firstName, o.firstName)
 .compare(this.email, o.email)
 .result();
 }
33. Bonus!
34. public static void main(String[] args) {
 
 Stopwatch stopwatch = Stopwatch.createStarted();
 
 List<Person> pers = PersonRepository.getByLimit(50);
 
 Iterable<PersonDto> dtos = from(pers).transform(personToDto);
 
 from(personDtos).forEach(printer);
 
 long nanos = stopwatch.elapsed(TimeUnit.NANOSECONDS);
 }
35. Preconditions
36. Preconditions goodness - Validate arguments - Check for null - Check elements in Lists, String or Array
37. import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
 
 public class PreconditionsSample { 
 public static void main(String[] args) { 
 checkState(args.length > 0, "Too less parameters”); 
 checkNotNull(args, "You have to pass some parameters");
 }
 }

38. Ordering
39. Ordering goodness - Ordering is a special Comparator instance - Guava’s fluent Comparator class - Chaining methods
40. Ordering<Person> bySuffix = new Ordering<Person>() {
 @Override
 public int compare(Person p1, Person p2) {
 return p1.getSuffix().compareTo(p2.getSuffix());
 }
 };
 Ordering<Person> byNameLength = new Ordering<Person>() {
 @Override
 public int compare(Person p1, Person p2) {
 return Ints.compare(p1.getName().length(), p2.getName().length());
 }
 };
 
 List<Person> persons = PersonRepository.instance().getByLimit(50);
 Collections.sort(persons, byNameLength.compound(bySuffix));
41. Collections
42. Collection goodness - New collections not included in JDK - Immutable collections
43. Why immutable? - Thread safe: no race conditions - More memory efficient that mutable alternative - Safe for use by untrusted libraries - Guava collection types doesn’t allow nulls
44. New collection types - Multiset - Multimap - BiMap - Table - ClassToInstanceMap - RangeSet
45. Multiset - Generalization of the notion of Set - Members allowed to appear more than once - Order is irrelevant
46. Multimap - Associates keys to arbitrary values - Alternative to Map<K, List<V>> or Map<K, Set<V>> A -> 1 A -> 2 A -> 4 B -> 3 C -> 5 A -> [1, 2, 4] B -> 3 C -> 5
47. Bimap - Map values back to keys - Alternative to keep in sync two Map<T>
48. 
 Person p1 = new Person("Alex", "Simonescu");
 Person p2 = new Person("Josh", "Block");
 
 BiMap<String, Person> emailPerson = HashBiMap.create();
 emailPerson.put("hello@alexsimo.com", p1);
 emailPerson.put("hello@joshblock.com", p2);
 
 String p1Email = emailPerson.inverse().get(p1);

49. Table - Really a Table collection. Surprised? - Implementations as: • HashBasedTable, • TreeBasedTable, • ImmutableBasedTable • ArrayTable
50. String[] names = {"Bob", "Alice", "Andy", "Carol", "Ben"};
 
 // Table of names
 Table<Character, Integer, String> table = HashBasedTable.create();
 
 // First letter is a row key, length is a column key
 for (String name : names) {
 table.put(name.charAt(0), name.length(), name);
 }
 
 // Value corresponding to the given row and column keys
 table.get('A', 5); // -> Alice
 table.get('B', 3); // -> Ben
 
 // Set of column keys that have one or more values in the table
 table.columnKeySet(); // -> [4, 5, 3]
 
 // View of all mappings that have the given row key
 table.row('A'); // -> {4=Andy, 5=Alice}
51. ClassToInstance - Map types to values of that type - No need of getInstance(Class<T>) and T putInstance(Class<T>, T)
52. ClassToInstanceMap<Number> numbers = MutableClassToInstanceMap.create();
 
 numbers.putInstance(Integer.class, Integer.valueOf(0));
 numbers.putInstance(Double.class, Double.valueOf(1));
 numbers.putInstance(Float.class, Float.valueOf(3)); double myNum = numbers.getInstance(Double.class);
54. Collection Utils
55. Collections hierarchy interface Iterable<T> interface Collection<T> interface Set<T> interface List<T> interface Queue<T>
56. Static Constructors 
 List<Person> list = Lists.newArrayList();
 
 
 Map<Integer, Person> map = Maps.newLinkedHashMap();
 
 
 Set<Person> set = Sets.newHashSet(repo.getByLimit(50));
 
 
 List<String> elements = Lists.newArrayList("alpha", "beta", "gamma");
57. Iterables 
 frequency(Iterable object)
 
 
 concat(Iterable<E>)
 
 
 partition(Iterable<E>)
 
 
 getFirst(Iterable<E>, default)
58. Iterables Collections style 
 addAll(Collection addTo, Iterable toAdd)
 
 
 removeAll(Iterable removeFrom, Collection toRemove)
 
 
 contains(Iterable, Object) get(Iterable, int) 
 
 retainAll(Iterable removeFrom, Collection toRetain)
59. Sets 
 union(Set, Set) intersection(Set, Set) difference(Set, Set) symmetricDifference(Set, Set) cartesianProduct(List<Set>) powerSet()
60. Functional
61. Functional goodness - Kind of functional style on Java - Still not Scala - Handy filtering and transforming collections
62. Functional concepts - Function <F, T> —> A => B - Predicate <T> —> T => Boolean
63. Sometimes imperative version is more readable, concrete and efficient. Functional danger zone
64. List<State> states = Lists.newArrayList(
 new State("MT", false),
 new State("ID", false),
 new State("WY", false),
 new State("SD", false),
 new State("NE", false),
 new State("WI", false),
 new State("IN", false),
 new State("TX", false),
 new State("CA", true),
 new State("AZ", true),
 new State("NM", true),
 new State("AR", true),
 new State("IL", true),
 new State("IA", true)); Predicate<State> withI = state -> state.getAbbreviation().startsWith("I");
 Predicate<State> isExpanded = state -> state.isExpanded();
 
 Collection<State> filtered = filter(states, or(withI, not(isExpanded)));
65. Function<Person, Person> emailToUpper = person -> {
 person.setEmail(person.getEmail().toUpperCase());
 return person;
 };
 
 Function<Person, String> toUsername = person -> {
 String[] chunks = person.getEmail().split("@");
 return chunks[0];
 };
 
 List<Person> people = getPeople();
 Collection<String> usernames = transform(people, compose(toUsername, emailToUpper));
66. Predicate<Person> isNotNull = Predicates.notNull();
 Predicate<Object> isPerson = Predicates.instanceOf(Person.class);
 Predicate<Person> startsWithA = person -> person.getName().toLowerCase().startsWith("a");
 Predicate<Person> hasCar = person -> person.getCar().isPresent();
 
 Function<Person, String> toCarName = person -> person.getCar().get().getName();
 
 ImmutableList<Person> people = ImmutableList.copyOf(getPeople());
 
 List<String> cars = FluentIterable
 .from(people)
 .filter(isNotNull)
 .filter(isPerson)
 .filter(startsWithA)
 .filter(hasCar)
 .transform(toCarName)
 .toList();
67. Concurrency
68. Concurrency goodness - Future <T> on steroids - Allows registering callback when finished - Provides more executors
69. ExecutorService executorService = Executors.newFixedThreadPool(1);
 ListeningExecutorService executor = MoreExecutors.listeningDecorator(executorService);
 
 ListenableFuture<String> future = executor.submit(() -> {
 Thread.sleep(1000);
 return "Task completed";
 });
 
 future.addListener(() -> runOnCompletion(), executor);

70. ExecutorService executorService = Executors.newCachedThreadPool();
 ListeningExecutorService executor = MoreExecutors.listeningDecorator(executorService);
 
 ListenableFuture<String> future = executor.submit(() -> {
 Thread.sleep(1000);
 return "Task completed";
 });
 
 Futures.addCallback(future, new FutureCallback<String>() {
 @Override
 public void onSuccess(String s) {
 System.out.println("Task succeed: " + s);
 }
 
 @Override
 public void onFailure(Throwable throwable) {
 System.out.println("Task failed");
 }
 }, executor);
71. Guava Darkside
72. Guava Darkside - Heavy library —> use Proguard or similar - Lot’s of utilities —> extract only needed
73. https://github.com/android10/arrow
74. https://github.com/alexsimo/toolbelt
75. Guava vs Java 8
76. Writing clean code is your responsibility
77. + Inspiring people
78. Questions?
79. Sample project https://github.com/alexsimo/guava-demo
80. Links • http://www.tfnico.com/presentations/google-guava • http://gdg-krakow.github.io/google-io-ext-2012-guava/ • http://www.baeldung.com/category/guava/ • https://robinst.github.io/guava-java8-presentation/#/
81. Thanks! @alexsimonescu