Constructor with Properties class TokenInfo( val tokenType: String, val identity: String (…) ) public final class TokenInfo { private final String tokenType; private final String identity; (…) public TokenInfo( String tokenType, String identity, (…)) { this.tokenType = tokenType; this.identity = identity; (…) } public final String getTokenType() { return tokenType; } public final String getIdentity() { return identity; } }
Getters and Setters class TokenInfo( val tokenType: String, val identity: String (…) ) public final class TokenInfo { private final String tokenType; private final String identity; (…) public TokenInfo( String tokenType, String identity, (…)) { this.tokenType = tokenType; this.identity = identity; (…) } public final String getTokenType() { return tokenType; } public final String getIdentity() { return identity; } }
Named arguments and optional values class TokenInfo( val tokenType: String = "auth", val identity: String, val expiration: Int? = null ) val token = TokenInfo(identity = "xxx") Immutable classes with optional fields? Constructors with lots of parameters Builder object
Data classes data class TokenInfo( val tokenType: String, val identity: String (…) ) public final class TokenInfo { (…) public String toString() { (…) } public int hashCode() { (…) } public boolean equals(Object var1) { (…) } public final TokenInfoId copy(String tokenType, String identity) { (…) } public final String component1() { (…) } public final String component2() { (…) } } Immutability made easier
Collections improvements List result = list.stream() .flatMap(o -> o.isPresent() ? Stream.of(o.get()) : Stream.empty()) .collect(Collectors.toList()); val result = list.filter { it != null } List result = list.stream() .flatMap(o → o.map(Stream::of) .orElseGet(Stream::empty)) .collect(Collectors.toList()); List result = list.stream() .flatMap(Optional::stream) .collect(Collectors.toList());
● Good documentation ● Short library ● Is there a general interest in Kotlin in the company? Kotlin community Android devs pushing for a change Learning cost ® BUT... (2)
● It's production! ● New technology, may have bugs ● Adds code “behind the courtains” ● Any weird behaviour affecting memory, garbage collection... Can affect Performance
● Same Java VM ● You can see compiled bytecode ● Decompile problematic code to Java and tune it ● Start a component in Java and then convert it to Kotlin Can affect Performance ® BUT...
● Extension functions are just a trick, no overhead ● Null checks are a small runtime overhead ● Platform and base libraries are the sane ● Kotlin library overhead not important for backend Can affect Performance ® BUT... (2)
● Same IDE: IntelliJ, Eclipse... ● Same build tools: Maven, Gradle... ● In a microservices architecture build time not so critical Seconds? Tooling problems ® BUT...
final vs. open Some Java libraries rely on dinamically creating subclasses ● Interceptors and other injection “black magic” Spring, Guice… ● Mocks: Mockito, Spock
Compiler plugins ® All-open not enough ● @Transactional problem (if no class annotation) Explicit open class and methods ● Mocks? Mockito 2.1.0 “inline mocks”: “incubating” Kotlin-runner library: explicit packages
const val ONE = 1 // MyObject(1) NO OBJECTS ALLOWED // Translated to: public static final class Constants { companion object { const val TWO = 2 // MyObject(2) NO OBJECTS ALLOWED // Translated to: inlined val THREE = MyObject(3) // Translated to private static // + Companion class with getter @JvmField val FOUR = MyObject(4) // Translated to public static final } } Constants: too many options? https://blog.egorand.me/where-do-i-put-my-constants-in-kotlin/
● Eclipse with Kotlin and Groovy tests just don’t work ● Eclipse incremental compilation a bit slow ● Some crashes when updating IntelliJ plugin ● Incremental build disabled by default in some versions Maven+Gradle ● Checkstyle, Findbugs… Tooling problems?
● Eclipse with Kotlin and Groovy tests just don’t work ● Eclipse incremental compilation a bit slow ● Some crashes when updating IntelliJ plugin ● Incremental build disabled by default in some versions Maven+Gradle ● Checkstyle, Findbugs… Tooling problems?
Multi-platform ● Javascript Kotlin wrapper for ReactJS ● Native Kotlin plugin for CLion Kotlin/Native iOS support Not only the JVM! KotlinConf app fully made with Kotlin
Yay or Nay? ● Controlled risk, but… worth it? ● What’s the benefit? Mostly syntatic sugar Productivity really improved??? How about thinking about PEOPLE instead of PRODUCTS?
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