This document discusses clean code practices for using lambdas in Java. It recommends encapsulating predicates and filter logic in local variables and helper methods to make code more readable and expressive. It also promotes techniques like pair programming and code reviews to help apply these principles to legacy code. Additional resources include a screencast of a workshop on clean lambdas and the presenter's tweets.

1. VictorRentea.ro
Enterprise Java Training
VictorRentea.ro
victor.rentea@gmail.com
@victorrentea
© Copyright Victor Rentea 2017
Victor Rentea
19 june 2017, Barcelona
Clean Lambdas

2. VictorRentea.ro
Spring, JavaEE, JPA/Hibernate
Clean Code, Architectures
Design Patterns
TDD, Coach, Coding Dojos
Java Performance, more...
Victor Rentea
Consultant, Technical Lead
Lead Architect for major IBM client
2
Independent Trainer
Clean Code Evangelist
Speaker
victor.rentea@gmail.com VictorRentea.ro@victorrentea
1000+ devs. 1500+ hrs. 5 yrs.

3. VictorRentea.ro
Clean Lambdas
Why Lambdas ?
3
They are cool

4. VictorRentea.ro4
But is the Code still Clean ?

5. VictorRentea.ro
Clean Lambdas
5
.filter(MyObj::isActive)
Expressive ?
or
Cryptic ?
.filter(order -> order.getOrderLines().stream()
.filter(line->line.isActive()).findFirst().isPresent())
.map(Order::getOrderLines)
.flatMap(List::stream)
.filter(orderLine -> orderLine.getCount().compareTo(new BigDecimal(“2”))
.collect(groupingBy(OrderLine::getProduct,
groupingBy(line->line.getOrder().getPaymentMethod(),
summingInt(OrderLine::getCount);
My own little
Clean Lambdas study

6. VictorRentea.ro
Encapsulate PredicatesLocal Variables
6
Predicate<Order> needsTracking = order -> order.getPrice() > 1000;
Set<Customer> customersToNotify = orders.stream()
.filter(deliveryDueBefore(warningDate).or(needsTracking))
.filter(this::hasLinesNotInStock)
.map(Order::getCustomer)
.collect(toSet());
class OrderLine { ...
public boolean isNotInStock() {
return status != Status.IN_STOCK;
}
}
public boolean hasLinesNotInStock(Order order) {
return order.getOrderLines().stream()
.anyMatch(OrderLine::isNotInStock);
}
public static Predicate<Order> deliveryDueBefore(Date date) {
return order -> order.getDeliveryDueDate().before(date);
}
http://bit.ly/2dFf2fi
Helper methods in this:: Helper getters in entities
Functions returning Predicates

7. VictorRentea.ro7
Clean Code in Java8
Try some lib?
if checked Ex, >2 params
jOOL, vavr,…
For more, check-out the screen cast of my Clean Lambdas workshop
at Voxxed Bucharest 2017, on my website 

8. VictorRentea.ro
Pair Programming
8
Peer Review!

9. VictorRentea.ro9
Peer Review!
Pair Programming

10. 12
How to
apply all
this in my
legacy
code
??
Where
can I read
more ?
LET’S
PRACTICE
!!!
©

11. VictorRentea.ro13
Screen cast of my “Clean
Lambdas Workshop” at
VoxxedDays Bucharest

Check out my tweets for more

12. VictorRentea.ro
Enterprise Java Training
VictorRentea.ro
victor.rentea@gmail.com
@victorrentea
© Copyright Victor Rentea 2017
Victor Rentea
19 june 2017, Barcelona
Clean Lambdas
https://github.com/victorrentea/clean-lambdas-jbcnconf.git