Once upon a time, there was a poor, innocent language. It was friendly and kind. Everything could have been nice and peaceful, but there was another language that was grumpy and mean. One day they met and started to argue about who the better language was…. This session compares the Java language with TypeScript. It discusses how common problems are solved with these languages. At the end, you’ll see who is the beauty and who is the beast.

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!
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