It's exhausting staying up to date with the evolution of Java and the myriad other JVM languages. Is it worth it? What do modern languages give us?

1. —
Trisha Gee (@trisha_gee)
Developer & Technical Advocate, JetBrains
Is Boilerplate Code
Really So Bad?

2. Most of the time
TL;DR
Yes

4. Code is Read More Than Written

5. “Indeed, the ratio of time spent reading
versus writing is well over 10 to 1. We are
constantly reading old code as part of the
effort to write new code. ...[Therefore,]
making it easy to read makes it easier to
write.”
Robert C. Martin, Clean Code: A Handbook of Agile
Software Craftsmanship

6. Hello World

7. Writing: Java & Kotlin

8. Writing: REPL

9. package com.mechanitis.demo.boilerplate.demo;
public class Main {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
println("Hello World!")
Reading: Java

10. package com.mechanitis.demo.boilerplate.demo
fun main(args: Array<String>) {
println("Hello")
}
println("Hello")
Reading: Kotlin

11. System.out.println("Hello World!")println("Hello World!")
Reading: JShell

12. Declaring Variables

13. Map<Integer, Customer> customers = new HashMap<Integer, Customer>();
Java 5
Map<Integer, Customer> customers = new HashMap<~>();

14. Java 7
Map<Integer, Customer> customers = new HashMap<>();

15. Java 10
var customers = new HashMap<Integer, Customer>();

16. Kotlin
val customers = HashMap<Int, Customer>()

17. var customers = new HashMap<Integer, Customer>();
Reading: Java
var customers = HashMap<Integer, Customer>()

18. val customers = HashMap<Int, Customer>()
Reading: Kotlin

19. Data Classes

20. Writing: Java

21. Writing: Kotlin

22. public class Customer {
private final String name;
private final int age;
@Override
public boolean equals(final Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
final Customer customer = (Customer) o;
if (age != customer.age) {
return false;
}
return name != null ? name.equals(customer.name) : customer.name == null;
}
@Override
public int hashCode() {
int result = name != null ? name.hashCode() : 0;
result = 31 * result + age;
return result;
}
@Override
public String toString() {
return "Customer{" +
"name='" + name + ''' +
", age=" + age +
'}';
}
private String getName() {
return name;
}
private int getAge() {
return age;
}
public Customer(final String name, final int age) {
this.name = name;
this.age = age;
}
}
Reading: Java

23. Reading: Kotlin
data class CustomerKotlin (val name: String, val age: Int)

24. Writing Code Is Not The Hard Bit

25. http://cr.openjdk.java.net/~briangoetz/
amber/datum.html

26. Casting

27. Java
Kotlin

28. JEP 305: Pattern Matching for
instanceof (Preview)

29. Nulls

30. Java
Kotlin
Java 8

31. Switch

34. var port = Integer.valueOf(portInputValue);
return switch (port) {
case 20 -> PortType.FTP;
case 80,8080 -> PortType.HTTP;
case 27017 -> PortType.DATABASE;
default -> {
if (port >= 20_001 && port <= 30_000) {
break PortType.SAFE;
} else if (port >= 9080 && port <= 9092) {
break PortType.BUSY;
} else {
break PortType.UNKNOWN;
}
}
};

35. Default parameter values

36. Java
Kotlin

37. Collections

38. Java
Kotlin
Groovy

39. Java
Kotlin
Groovy

40. Lambda Expressions

41. Java
Kotlin

42. Functional Parameters

43. Java 8

44. Java 8

45. Kotlin

46. Navigating Collections

47. Java 8
Kotlin
Kotlin

48. Can we go too far?

49. Dangers of var/val
Customer c = CustomerFactory.create("Sam");Customer c = create("Sam");var c = create("Sam");

50. Implicits in Scala

51. When Is Boilerplate Code Good?

52. Kotlin
Kotlin

53. Groovy
def 'emits an event for new projects'() {
@Subject
def service = new EventService()
given:
def subscriber = Mock(Subscriber)
subscriber.onSubscribe(_) >> { Subscription sub -> sub.request(MAX_VALUE) }
Flux<Schedule.Project> projects = service.getProjects();
projects.subscribe(subscriber)
when:
service.recordNewActivity(schedule)
then:
1 * subscriber.onNext(schedule.projects[0])
}

54. In Summary

55. Elimination of Boilerplate Can
Improve Readability
You can focus on the business logic

56. data class CustomerKotlin (val name: String, val age: Int)

57. Not All “Boilerplate” is Boilerplate
…and removing it can change the meaning

58. val emails = customers.asSequence()
.filter { it.name.startsWith("A") }
.map { it.email }
.toList()
val emails = customers
.filter { it.name.startsWith("A") }
.map { it.email }

59. Less Code Is Not Always Better
Additional code can improve readability

60. def 'emits an event for new projects'() {
@Subject
def service = new EventService()
given:
def subscriber = Mock(Subscriber)
subscriber.onSubscribe(_) >> { Subscription sub -> sub.request(MAX_VALUE) }
Flux<Schedule.Project> projects = service.getProjects();
projects.subscribe(subscriber)
when:
service.recordNewActivity(schedule)
then:
1 * subscriber.onNext(schedule.projects[0])
}

61. Readability is subjective
…and is often related to familiarity

62. List<String> emails = customers.stream()
.filter(customer -> customer.getName().startsWith("A"))
.map(CustomerJava::getEmail)
.collect(toList());
List<String> emails = new ArrayList<>();
for (CustomerJava customer : customers) {
if (customer.getName().startsWith("A")) {
String email = customer.getEmail();
emails.add(email);
}
}

63. Modern languages offer the option to
reduce code
Will this make it more readable?

64. http://bit.ly/BoilJVM