The document discusses the relevance of Scala in the context of Java 8 and beyond, addressing key features like lambdas, traits, and type inference that Scala offers compared to Java. It outlines the historical gap between Java and Scala and how Java 8 has narrowed this gap while still maintaining Scala's unique advantages. Key takeaways include Scala's powerful pattern matching, implicits, and traits that enhance code functionality and readability, making it a relevant choice for modern backend engineering.

1. Java 8 and Beyond,
a Scala Story
Ittai Zeidman, September 2016
http://searchengineland.com/figz/wp-content/seloads/2015/06/evolution-seo-marketer-ss-1920.jpg

2. Ittai Zeidman
• @ittaiz
• Backend Engineering Lead @
Wix
• Clean Code Fanatic
• Scala lover
• Proud spouse and father of 3

3. Ittai Zeidman
• @ittaiz
• Backend Engineering Lead @
Wix
• Clean Code Fanatic
• Scala lover
• Proud spouse and father of 3

4. Preface

5. Preface
• Java 8 was released
in 2014

6. Preface
• Java 8 was released
in 2014
• Which begs the
question…
• Is Scala still relevant?

7. Preface
• Java 8 was released
in 2014
• Which begs the
question…
• Is Scala still relevant?
– Yes.

8. Preface
• Java 8 was released
in 2014
• Which begs the
question…
• Is Scala still relevant?
– Yes.

9. Preface
• Java 8 was released
in 2014
• Which begs the
question…
• Is Scala still relevant?
– Yes.
– This talk is about
convincing you!

10. Quick Agenda
• A bit of history
– The Java-Scala gap
– How Java 8 reduces it
– Remaining gaps
• A deeper dive into:
– Traits
– Type Inference
– Pattern matching
– Implicits

11. The Java-Scala gap (pre Java
8)Scala’s big selling
points:
• Lambdas
• Collections library
• Traits
• Type inference
• DSLs
• Implicits

12. The Java-Scala gap
(currently)Scala’s big selling
points:
• Lambdas
• Collections library
• Traits
• Type inference
• DSLs
• Implicits

13. There’s So Much More…

14. There’s So Much More…
For-comprehensions
Flexible scoping
Built-in tuples
Higher-kinded types
Declaration-site
variance
Macros
Bottom types
Structural types
Type members
Path-dependent types
Implicit conversions

15. RIGHT.
WHY SHOULD YOU CARE?

16. #1: TRAITS

17. Ye Olde Logging
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class ClassWithLogs {
private static Logger log =
LoggerFactory.getLogger(ClassWithLogs.class);
public String getNormalizedName(Person person) {
log.info("getNormalizedName called");
log.debug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
log.debug("Normalized name is: " + normalizedName);
return normalizedName;
}
}

18. Ye Olde Logging
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class ClassWithLogs {
private static Logger log =
LoggerFactory.getLogger(ClassWithLogs.class);
public String getNormalizedName(Person person) {
log.info("getNormalizedName called");
log.debug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
log.debug("Normalized name is: " + normalizedName);
return normalizedName;
}
}
Boilerplate

19. Ye Olde Logging
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class ClassWithLogs {
private static Logger log =
LoggerFactory.getLogger(ClassWithLogs.class);
public String getNormalizedName(Person person) {
log.info("getNormalizedName called");
log.debug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
log.debug("Normalized name is: " + normalizedName);
return normalizedName;
}
}
Eager
Evaluation
Boilerplate

20. Ye Olde Logging
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class ClassWithLogs {
private static Logger log =
LoggerFactory.getLogger(ClassWithLogs.class);
public String getNormalizedName(Person person) {
log.info("getNormalizedName called");
log.debug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
log.debug("Normalized name is: " + normalizedName);
return normalizedName;
}
}
Eager
Evaluation
Boilerplate

21. Improvement?
public class LoggingSample implements Logging {
public String getNormalizedName(Person person) {
logInfo("getNormalizedName called");
logDebug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
logDebug("Normalized name is: " +
normalizedName);
return normalizedName;
}
}

22. Improvement?
public class LoggingSample implements Logging {
public String getNormalizedName(Person person) {
logInfo("getNormalizedName called");
logDebug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
logDebug("Normalized name is: " +
normalizedName);
return normalizedName;
}
}

23. Improvement?
public class LoggingSample implements Logging {
public String getNormalizedName(Person person) {
logInfo("getNormalizedName called");
logDebug("Normalizing " + person.toString());
String normalizedName =
person.getName().toUpperCase().trim();
logDebug("Normalized name is: " +
normalizedName);
return normalizedName;
}
}

24. Java Interface Limitations

25. Java Interface Limitations
• No fields allowed

26. Java Interface Limitations
• No fields allowed
– Need Logger instance

27. Java Interface Limitations
• No fields allowed
– Need Logger instance
– Workaround: getter
public interface Logging {
Logger logger();
default void logDebug(String msg)
{
if (logger().isDebugEnabled())
logger().debug(msg);
}
default void logInfo(String msg) {
if (logger().isInfoEnabled())
logger().info(msg);
}
}

28. Java Interface Limitations
• No fields allowed
– Need Logger instance
– Workaround: getter
– But... boilerplate :-(
public interface Logging {
Logger logger();
default void logDebug(String msg)
{
if (logger().isDebugEnabled())
logger().debug(msg);
}
default void logInfo(String msg) {
if (logger().isInfoEnabled())
logger().info(msg);
}
}

29. Java Interface Limitations
• No fields allowed
– Need Logger instance
– Workaround: getter
– But... boilerplate :-(
• Only public methods
– Logging APIs visible!
– … as is logger()
public interface Logging {
Logger logger();
default void logDebug(String msg)
{
if (logger().isDebugEnabled())
logger().debug(msg);
}
default void logInfo(String msg) {
if (logger().isInfoEnabled())
logger().info(msg);
}
}

30. And Lazy Evaluation?

31. And Lazy Evaluation?
• Can be implemented with a lambda:
import java.util.function.Supplier;
default void logDebug(Supplier<String> message) {
if (getLogger().isDebugEnabled())
getLogger().debug(message.get());
}

32. And Lazy Evaluation?
• Can be implemented with a lambda:
import java.util.function.Supplier;
default void logDebug(Supplier<String> message) {
if (getLogger().isDebugEnabled())
getLogger().debug(message.get());
}
• But there’s boilerplate at the call site:
logDebug(() -> "Normalizing " +
person.toString());

33. Scala Traits
trait Logging {
private val logger =
LoggerFactory.getLogger(getClass)
protected def logWarn(msg: => String) =
if (logger.isWarnEnabled)
logger.warn(msg)
protected def logDebug(msg: => String) =
if (logger.isDebugEnabled)
logger.debug(msg)
}

34. Scala Traits
• Allow fields
trait Logging {
private val logger =
LoggerFactory.getLogger(getClass)
protected def logWarn(msg: => String) =
if (logger.isWarnEnabled)
logger.warn(msg)
protected def logDebug(msg: => String) =
if (logger.isDebugEnabled)
logger.debug(msg)
}

35. Scala Traits
• Allow fields
• Participate in
lifecycle
trait Logging {
private val logger =
LoggerFactory.getLogger(getClass)
protected def logWarn(msg: => String) =
if (logger.isWarnEnabled)
logger.warn(msg)
protected def logDebug(msg: => String) =
if (logger.isDebugEnabled)
logger.debug(msg)
}

36. Scala Traits
• Allow fields
• Participate in
lifecycle
• Support
visibility
trait Logging {
private val logger =
LoggerFactory.getLogger(getClass)
protected def logWarn(msg: => String) =
if (logger.isWarnEnabled)
logger.warn(msg)
protected def logDebug(msg: => String) =
if (logger.isDebugEnabled)
logger.debug(msg)
}

37. Scala Traits
• Allow fields
• Participate in
lifecycle
• Support
visibility
• Multiple
inheritance!
trait Logging {
private val logger =
LoggerFactory.getLogger(getClass)
protected def logWarn(msg: => String) =
if (logger.isWarnEnabled)
logger.warn(msg)
protected def logDebug(msg: => String) =
if (logger.isDebugEnabled)
logger.debug(msg)
}

38. Scala Traits
• Allow fields
• Participate in
lifecycle
• Support
visibility
• Multiple
inheritance!
• By Name
eval
trait Logging {
private val logger =
LoggerFactory.getLogger(getClass)
protected def logWarn(msg: => String) =
if (logger.isWarnEnabled)
logger.warn(msg)
protected def logDebug(msg: => String) =
if (logger.isDebugEnabled)
logger.debug(msg)
}

39. #2: TYPE INFERENCE
*https://visualizingreading.wikispaces.com/file/view/Detective2.gif/214220534/358x190/Detective2.gif

40. Type Inference

41. Type Inference
• …the analysis of a program to infer the
types of some or all expressions, usually
at compile time…

42. Type Inference
• …the analysis of a program to infer the
types of some or all expressions, usually
at compile time…
• A balance between Compile Time Safety
and Verbosity

43. Java’s Type Inference

44. Java’s Type Inference
• Generics class ClassWithGenerics {
<T> void generic(T param) {
println(someParameter);
}
}
...
generic(“some param”)
generic(5)

45. Java’s Type Inference
• Generics
• Project Coin
class ClassWithGenerics {
<T> void generic(T param) {
println(someParameter);
}
}
...
generic(“some param”)
generic(5)
Map<String, Int> keyCounter =
new HashMap<>();

46. Scala’s Type Inference

47. Scala’s Type Inference
• Generics

48. Scala’s Type Inference
• Generics
• Local variables

49. Scala’s Type Inference
• Generics
• Local variables
• Method return values

50. LET’S DIVE INTO SOME CODE

51. #3: PATTERN MATCHING

52. Java’s Switch Statement

53. Java’s Switch Statement
• Switch statement is incredibly limited
– Only supports primitives (and strings)
– No arbitrary expressions (e.g. guards)
– No result values

54. Java’s Switch Statement
• Switch statement is incredibly limited
– Only supports primitives (and strings)
– No arbitrary expressions (e.g. guards)
– No result values
• Workarounds are ugly
– Nested control structures
– Encoding enums instead of using types

55. Pattern Matching
• Pattern matching in
Scala:

56. Pattern Matching
• Pattern matching in
Scala:
– Allows arbitrary types

57. Pattern Matching
• Pattern matching in
Scala:
– Allows arbitrary types
– Supports guards

58. Pattern Matching
• Pattern matching in
Scala:
– Allows arbitrary types
– Supports guards
– Checks for
exhaustiveness

59. Pattern Matching
• Pattern matching in
Scala:
– Allows arbitrary types
– Supports guards
– Checks for
exhaustiveness
– User-extensible

60. Pattern Matching
• Pattern matching in
Scala:
– Allows arbitrary types
– Supports guards
– Checks for
exhaustiveness
– User-extensible
– Ubiquitous

61. LET’S DIVE INTO SOME CODE

62. #4: IMPLICITS

63. Passing Class info (generics)

64. Passing Class info (generics)
• Java’s idiom is passing Class<T> clazz
around

65. Passing Class info (generics)
• Java’s idiom is passing Class<T> clazz
around
• Scala supports implicit parameters
– These are filled in by the compiler
– Well-defined rules for implicit search

66. Enhancing third party code

67. Enhancing third party code
• Java’s idiom is verbose wrapper methods

68. Enhancing third party code
• Java’s idiom is verbose wrapper methods
• Scala supports implicit methods
– Verified at compile time

69. LET’S DIVE INTO SOME CODE

70. Scala’s Relevance

71. Scala’s Relevance
• Post Java 8

72. Scala’s Relevance
• Post Java 8 ✔

73. Scala’s Relevance
• Post Java 8
• Towards Java 9
✔

74. Scala’s Relevance
• Post Java 8
• Towards Java 9
✔
✔

75. Scala’s Relevance
• Post Java 8
• Towards Java 9
• Java 10
✔
✔

76. Scala’s Relevance
• Post Java 8
• Towards Java 9
• Java 10
✔
✔
?

77. QUESTIONS?
?
?
?
?
?
?
?
?
?
?

78. WE’RE DONE
HERE!
Thank you for listening
@ittaiz
http://il.linkedin.com/in/ittaiz
Sample Code:
https://github.com/ittaiz/scala-and-java8