1. Karakun DevHub_
dev.karakun.com
@net0pyr / @HendrikEbbers

2. Once upon a time in
Coderland…
Once upon a time in
Coderland…
@net0pyr / @HendrikEbbers

3. … lived a young coder that found this
cool new language TypeScript

4. But one day the coder got lost in the woods of
Coderland and found a magical old castle…

5. And after a while the coder and the
beast get to know each other…
In the castle lived a beast the coder had never seen before

6. And after a while the coder and the
beast got to know each other…

7. Beauty and
the Beast
@net0pyr / @HendrikEbbers

8. Karakun DevHub_
dev.karakun.com
About me
• Karakun Co-Founder
• Lead of JUG Dortmund
• JSR EG member
• JavaOne Rockstar, Java Champion
• AdoptOpenJDK TSC
@net0pyr / @HendrikEbbers

9. Karakun DevHub_
dev.karakun.com
About me
• Karakun Co-Founder
• Lead of JUG Freiburg
• Used to be: speaker, author,
developer, …
• Switched to the dark side
@net0pyr / @HendrikEbbers

10. Karakun DevHub_
dev.karakun.com
Java
• "Oak" (Object Application Kernel) / "The Green
Project" was developed in 1992 at Sun
Microsystems
• This project evolved to Java in 1995
@net0pyr / @HendrikEbbers

11. Karakun DevHub_
dev.karakun.com
Java
• In 1998 the JCP (Java Community
Project) was formed
• Java is released under GNU GPL with
classpath exception
• Java is 100% open source (OpenJDK)
and several vendors provide JDKs
@net0pyr / @HendrikEbbers

12. Karakun DevHub_
dev.karakun.com
TypeScript
• First public appearance in 2012
• Developed by Microsoft
• Open-source
• Strict superset of JavaScript, adds optional
static typing
• Transcompiles to JavaScript
@net0pyr / @HendrikEbbers

13. primitive
datatypes
@net0pyr / @HendrikEbbers

14. Karakun DevHub_
dev.karakun.com
Variables
let isDone: boolean = false;
boolean isDone = false;
@net0pyr / @HendrikEbbers

15. Karakun DevHub_
dev.karakun.com
Variables
let isDone: boolean = false;
boolean isDone = false;
Type Name Value
@net0pyr / @HendrikEbbers

16. Karakun DevHub_
dev.karakun.com
Variables
let isDone: boolean = false;
boolean isDone = false;
ValueTypeName
@net0pyr / @HendrikEbbers

17. Karakun DevHub_
dev.karakun.com
Primitive Datatypes
boolean v = false;
int v = 1;
long v = 1L;
double v = 1.0d;
float v = 1.0f;
short v = 1;
byte v = 1;
char v = 'a';
let v: number = 6;
let v: boolean = true;
let v: string = "Hi";
@net0pyr / @HendrikEbbers

18. Karakun DevHub_
dev.karakun.com
Primitive Datatypes
• JavaScript numbers are always 64-bit floating
point
• Same behaviour in TypeScript
var x = 999999999999999; // x will be 999999999999999
var y = 9999999999999999; // y will be 10000000000000000
var x = 0.2 + 0.1; // x will be 0.30000000000000004
@net0pyr / @HendrikEbbers

19. Karakun DevHub_
dev.karakun.com
Primitive Datatypes
• String is not a primitive datatype in Java (see
java.lang.String)
• Java allows to create a String like primitive data
• Internally the String class holds a char[]
@net0pyr / @HendrikEbbers

20. Karakun DevHub_
dev.karakun.com
Arrays and tuples
• TypeScript provides native support for arrays and tuples
• Java provides native support for arrays
let vArray: number[] = [1, 2, 3];
let vTuple: [string, number];
int[] vArray = {1, 2, 3};
@net0pyr / @HendrikEbbers

21. Karakun DevHub_
dev.karakun.com
Arrays and tuples
• Instead of providing native tuples in the Java
language syntax a more extensive feature is
planed for future Java versions
• With Records (JEP 169) you can easily create
constructs like tuples (and much more)
@net0pyr / @HendrikEbbers

22. methods and
functions
@net0pyr / @HendrikEbbers

23. Karakun DevHub_
dev.karakun.com
Methods / Functions
function isBig(x: number): boolean {
return x > 10;
}
boolean isBig(int x) {
return x > 10;
}
@net0pyr / @HendrikEbbers

24. Karakun DevHub_
dev.karakun.com
Methods / Functions
function isBig(x: number): boolean {
return x > 10;
}
Param Name Param Type Return Type
boolean isBig(int x) {
return x > 10;
}
@net0pyr / @HendrikEbbers

25. Karakun DevHub_
dev.karakun.com
Methods / Functions
function isBig(x: number): boolean {
return x > 10;
}
boolean isBig(int x) {
return x > 10;
}
Param NameParam TypeReturn Type
@net0pyr / @HendrikEbbers

26. Karakun DevHub_
dev.karakun.com
Function as a type
const f = (n: number): number => n * n;
handle(f);
• In TypeScript functions are first-class citizens
@net0pyr / @HendrikEbbers

27. Karakun DevHub_
dev.karakun.com
Functional Interface
@FunctionalInterface
public interface Square {
int square(int n);
}
Square f = (n) -> n * n;
handle(f);
• In Java similar functionality can be created by
using functional interfaces
@net0pyr / @HendrikEbbers

28. object oriented
programming
@net0pyr / @HendrikEbbers

29. Karakun DevHub_
dev.karakun.com
Classes
class Animal {
move(distance: number = 0) {
console.log(`Animal moved ${distance} m.`);
}
}
public class Animal {
public void move(int distance) {
System.out.println("Animal moved " + distance + "m");
}
}
@net0pyr / @HendrikEbbers

30. Karakun DevHub_
dev.karakun.com
Access modifiers
• You might have noticed the missing access
modifier in TypeScript.
• If you do not define an access modifier, TypeScript
automatically uses the public modifier
• Both languages know the public, protected
and private modifiers
@net0pyr / @HendrikEbbers

31. Karakun DevHub_
dev.karakun.com
Access modifiers
• In Java the protected modifier allows access
from inherited classes or from within the same
package
• Since we do not have package structures in
TypeScript the protected modifier only allows
access from inherited classes
@net0pyr / @HendrikEbbers

32. Karakun DevHub_
dev.karakun.com
Interfaces
• Both TypeScript and Java support interfaces
• We can see in the sample that TypeScript has a
different approach to handle data access
interface Countdown {
name: string;
start(sec: number): void;
}
public interface Countdown {
String getName();
void setName(String name);
void start(long sec);
}
@net0pyr / @HendrikEbbers

33. Karakun DevHub_
dev.karakun.com
Mutable data
class Person {
name : string;
}
public class Person {
private String name;
public void setName(String n) {this.name = n;}
public String getName() {return this.name;}
}
@net0pyr / @HendrikEbbers

34. Karakun DevHub_
dev.karakun.com
Immutable data
class Person {
readonly birthday : Date;
}
public class Person {
private final Date birthday;
public Person(Date birthday) {this.birthday = birthday;}
public Date getBirthday() {return this.birthday;}
}
@net0pyr / @HendrikEbbers

35. Karakun DevHub_
dev.karakun.com
Easier data access in Java
• With Records (JEP 359) Java will contain additional
functionality to define data classes in the future
• Properties will still be accessed by setter/
getter methods but such methods do not need
to be implemented any more.
@net0pyr / @HendrikEbbers

36. Karakun DevHub_
dev.karakun.com
Abstraction and Inheritance
abstract class Animal {
abstract makeSound(): void;
}
public abstract class Animal {
public abstract void makeSound();
}
@net0pyr / @HendrikEbbers

37. Karakun DevHub_
dev.karakun.com
Abstraction and Inheritance
class Dog extends Animal {
makeSound(): void {console.log("WUFF");}
}
public class Dog extends Animal {
public void makeSound() {System.out.println("WUFF");}
}
@net0pyr / @HendrikEbbers

38. Karakun DevHub_
dev.karakun.com
Generics
interface Player<T extends Media> {
play(media : T);
}
public interface Player<T extends Media> {
public void play(T media);
}
@net0pyr / @HendrikEbbers

39. Karakun DevHub_
dev.karakun.com
Reflection
• Java provides a powerful reflection API
• Reflection can be used to inspect code at runtime
• Reflection can be used to modify the runtime behavior
Method m = foo.getClass().getMethod("play", String.class);
m.invoke(foo, "medley.mp3");
@net0pyr / @HendrikEbbers

40. Karakun DevHub_
dev.karakun.com
Reflection Sample
class Demo {
public foo: number = 1;
}
console.log(Reflect.has(demo, "foo"));
console.log(Reflect.has(demo, "bar"));
@net0pyr / @HendrikEbbers
• TypeScript does not provide a stable reflection API

41. Karakun DevHub_
dev.karakun.com
Annotations
• Java provides annotations to apply metadata
• Annotations in Java can be accessed at compile time
or runtime
• Annotations in Java are heavily bound to reflections
@Singleton
public class DatabaseService {
}
@net0pyr / @HendrikEbbers

42. Karakun DevHub_
dev.karakun.com
Decorators Sample
function LogMethod(target: any) {
console.log(target);
}
class Demo {
@LogMethod
public foo() {}
}
@net0pyr / @HendrikEbbers

43. Karakun DevHub_
dev.karakun.com
Decorators Sample
function LogMethod(target: any) {
console.log(target);
}
class Demo {
@LogMethod
public foo() {}
}
Method with same name is
called automatically
No Concrete annotation
definition
@net0pyr / @HendrikEbbers

44. functional
programming
@net0pyr / @HendrikEbbers

45. Karakun DevHub_
dev.karakun.com
Functional Programming
@net0pyr / @HendrikEbbers

46. Karakun DevHub_
dev.karakun.com
Functional-ish Programming
@net0pyr / @HendrikEbbers
+ Libraries + Libraries

47. Karakun DevHub_
dev.karakun.com
Functional-ish Programming
@net0pyr / @HendrikEbbers
• Immutable data structures
• Pure functions
• Result depends only on parameters
• No side-effects

48. Karakun DevHub_
dev.karakun.com
Immutable objects
@net0pyr / @HendrikEbbers
interface Person {
readonly name: string;
}
public interface Person {
private final String name;
... more Code required
}

49. Karakun DevHub_
dev.karakun.com
Readonly ≠ Immutable
@net0pyr / @HendrikEbbers
function evilRename(person: any) {
person.name = "Mailer";
}
const p: Person = { name: "Müller" };
evilRename(p);
console.log(p.name);
prints Mailer

50. Karakun DevHub_
dev.karakun.com
Creating immutable objects
@net0pyr / @HendrikEbbers
const p1: Person = { name: "Müller" };
const p2: Person = { ...p1, name: "Maier" }
final Person p1 = new Person("Müller");
Final Person p2 = p1.withName("Müller");
requires a lot of boilerplate

51. Karakun DevHub_
dev.karakun.com
Immutable collections
@net0pyr / @HendrikEbbers
const n1: ReadonlyArray<number> = [ 1, 2, 3 ];
const n2: ReadonlyArray<number> = [ ...n1, 4 ];
import io.vavr.collection.Vector;
final Vector<Integer> n1 = Vector.ofAll(1, 2, 3);
Final Vector<Integer> n2 = n1.append(4);

52. Karakun DevHub_
dev.karakun.com
Pure Functions
@net0pyr / @HendrikEbbers
Responsibility of the developer
VAVR, Java Streams, RxJava
Lodash, RxJS

53. but there’s
more
@net0pyr / @HendrikEbbers

54. Karakun DevHub_
dev.karakun.com
Template Strings
@net0pyr / @HendrikEbbers
const s = `Hello ${name}!
How are you?`
Text blocks, rest planned…

55. Karakun DevHub_
dev.karakun.com
Type Alias & Union Types
@net0pyr / @HendrikEbbers
type Fruit = Apple | Banana | Strawberry;
function search(id: number): Person | Error {
...
}

56. Karakun DevHub_
dev.karakun.com
Type Alias & Union Types
@net0pyr / @HendrikEbbers
type Greeting = "Hello" | "Aloha";
let s: Greeting;
s = "Hello";
s = "Bonjour";
Does not compile

57. Karakun DevHub_
dev.karakun.com
Strict null checks
@net0pyr / @HendrikEbbers
let s: String;
S = null;
console.log(s.length);
let s: String | null;
s = null;
console.log(s.length);
Compiler Flag: strictNullChecks
Does not compile
Does not compile

58. Karakun DevHub_
dev.karakun.com
Strict null checks
@net0pyr / @HendrikEbbers
...
• Optional
• @NonNull, @Nullable

59. Karakun DevHub_
dev.karakun.com
Deconstruction
@net0pyr / @HendrikEbbers
const { firstName, lastName } = person;
console.log(firstName, lastName};
const { lastName: name } = person;
console.log(name);
const { address: { street } } = person;
console.log(street);

60. Karakun DevHub_
dev.karakun.com
Deconstruction
@net0pyr / @HendrikEbbers
return switch(n) {
case IntNode(int i) -> i;
case AddNode(Node left, Node right) -> left + right;
};
• Will be available for records in a future version

61. … and they lived happily
ever after

62. Happy End

63. Karakun@
- Beauty and the Beast: Java Versus TypeScript
- Not Dead Yet: Java on the Desktop
- Productivity Beyond Failure
- JavaFX Real-World Applications
- Team Diversity the Successful Way
- Rich Client Java: Still Going Strong!
Sessions
& StickersSocialize
dev.karakun.com