Java moderno java para Jedis episodio I

Modern Java: Java for Jedis
Episode I
Roan Brasil Monteiro

Speaker/Jedi
2
Roan Brasil
@roanbrasil
Senior Engineer
+ JCP-Member
+ Open Source Contributor
+ Book and blog writer
+ Teacher

Summary
3
Java
• Lambdas expressions
• Method references
• Functional interfaces
• Stream API
• Default methods
• Optional class
• Date/Time API

Lambdas Expressions : Definition
Java - Functionalities
4
● Representation of one anonymous function
Anonymous : We say anonymous because it doesn't have an explicit name like a method
would normally have; less to write and think about
Function : We say function, because a lambda isn't associate with particular class like
method is. But like a method, a lambda has a list of parameters, a body, a return type, and a
possible list of exceptions that can be thrown.
Passed around : A lambda expression can be passed as argument to a method or stored in
a variable.
Concise : You do not need to write a lot of boilerplate.
Credits -> Definition from the book Modern Java in Action

Lambdas Expressions : Before and Later
5
● Before
● Later
Lambda is composed by 3 parts:
Definition from the book Modern Java in Action

Lambdas Expressions : Quiz
6
What lambdas expressions are not corrected?
Quiz Lambda Syntax
1. () -> {}
2. () -> “Yoda”
3. () -> { return “Jedi”; }
4. (Integer i) -> return “Jedi” + i;
5. (String s) -> { “Star Wars”; }

7
What lambdas expressions are not corrected?
Quiz Lambda Syntax
1. () -> {}
2. () -> “Yoda”
3. () -> { return “Jedi”; }
4. (Integer i) -> return “Jedi” + i;
5. (String s) -> { “Star Wars”; }

Lambdas Expressions : Why?
8
Syntax
Why ?
It is necessary use braces*
The “Star Wars” is an expression, it is not a statement. There are two ways to do that.
(Integer i) -> return “Roan” + i;
(Integer i) -> { return “Roan”+ i;}
(String s) -> { “Star Wars’;}
(String s) -> “Star Wars”
(String s) -> { return “Star Wars”; }
Exception method void
process(() -> System.out.println(“Roan"));

Lambdas Expressions : Some examples
9

Lambdas Expressions: Quiz
10
Quelles sont les expressions lambdas correctes ?
Quiz Lambda Syntax
execute(() -> {});
public void execute(Runnable r) {
r.run();
}
public Callable<String> fetch(){
return () -> “Joker Exemple ☺”;
}
Predicate<Apple> p = (Apple a) -> a.getWeight();

11
Quelles sont les expressions lambdas correctes ?
Quiz Lambda Syntax
execute(() -> {});
public void execute(Runnable r) {
r.run();
}
public Callable<String> fetch(){
return () -> “Joker Exemple ☺”;
}
Predicate<Apple> p = (Apple a) -> a.getWeight();
(Apple a) -> a.getWeight(); a de signature (Apple) -> Integer e le Predicate<Apple> attends (Apple) -> boolean

Functional Interfaces : Definition and Examples
12
● Functional Interface are interfaces with just an abstract method without or with the annotation
@FunctionalInterface

Functional Interfaces: More Example
13

Functional Interfaces : Examples
14

Functional Interfaces : Examples
15
●
Predicate<Integer> IntPredicate
Performance
Boxing
Unboxing

Functional Interfaces: Examples Table
16

Functional Interfaces: Quiz
17
What are each functional interfaces below?
Quiz
1. T -> R
2. (int, int) -> int
3. T -> void
4. () -> T
5. (T, U) -> R
1. Function<T, R>
2. IntBinaryOperator
3. Consumer<T>
4. Supplier<T>
5. BiFunction<T, U, R>

Functional Interfaces: Examples
18

● Example:
Method Reference
19
Beneficiar de uma melhor leitura de código
Thanks for this operator « :: » (classe::méthode)
Define an abstract method from une functional interface

Method Reference: Example
20

API Stream
21
package java.util.stream
https://github.com/roanbrasil/clean-code-tdc/blob/master/src/main/java/com/tdc/cleancode/stream_api/StreamsExample.java

Classe Optional: Déjà vu
22

Classe Optional: Hadouken
23
https://github.com/roanbrasil/clean-code-tdc/blob/master/src/main/java/com/tdc/cleancode/optional/before/BeforeOptional.java

Classe Optional: Hadouken
24
https://github.com/roanbrasil/clean-code-tdc/blob/master/src/main/java/com/tdc/cleancode/optional/after/AfterOptional.java

● Some util methods, one of we use a lot :
Classe Optional
25
Optional.of (objet non nullable) Optional.ofNullable (objet nullable)
isPresent() isEmpty()
orElse() orElseThrow()
get()
filter()
map() flatMap()

API Date/Time
26
Start from 1900
It's not a date
It is point in a time with some
precision in millisecondes
The months starts with the
index 0 a 11
Timezone CET (Central Europe Time)
Use a library externe like
JodaTime
DateFormat no thread-safe
Date et Dateformat are
mutable

● There are few classes form new Api Date/Time, such as LocalDate, LocalDateTime, Instant, LocalTime, Duration and
Period.
● Example of code :
API Date/Time
27

● Exemple de code :
API Date/Time
28

● Example de code :
API Date/Time
29
https://github.com/roanbrasil/clean-code-tdc/blob/master/src/main/java/com/tdc/cleancode/java_time_api/before/BeforeJava8JavaTimeApi.java
https://github.com/roanbrasil/clean-code-tdc/blob/master/src/main/java/com/tdc/cleancode/java_time_api/after/AfterJava8JavaTimeApi.java

● Create direct methods from interfaces with the key word « default »
● Exemple :
public interface Step {
void execute (Information information);
default String fallback(){
return "ERRO";
}
}
Default Methods
30

Java moderno java para Jedis episodio I

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Java moderno java para Jedis episodio I