This document discusses new features in Java 8 including lambda expressions, annotations on Java types, date and time API improvements, and functional programming concepts. It focuses on how Java 8 enables functional programming through lambda expressions, higher order functions in collections/streams, and virtual extension methods. The document provides examples and recommendations for adopting functional programming approaches in Java code.

1. Live
Coding:
By
Urs
Peter
upeter@xebia.com
@urs_peter

2. New
Features
of
Java
8
• JSR
335
Lambda
Expressions
and
Virtual
Extension
Methods
• JSR
308
AnnotaJons
on
Java
Types
Map<@NonNull String, @NonEmpty List<@Readonly Document>> files;!
• JSR
310
Date
and
Time
API
OffsetDateTime now = OffsetDateTime.now();
System.out.println(now.format(DateTimeFormatter.ISO_DATE));!

3. New
Features
of
Java
8
• JSR
335
Lambda
Expressions
and
Virtual
Extension
Methods
• JSR
308
AnnotaJons
on
Java
Types
Map<@NonNull String, @NonEmpty List<@Readonly Document>> files;!
• JSR
310
Date
and
Time
API
OffsetDateTime now = OffsetDateTime.now();
System.out.println(now.format(DateTimeFormatter.ISO_DATE));!

4. New
Features
of
Java
8
• JSR
335
Lambda
Expressions
and
Virtual
Extension
Methods
FuncAonal
MulAple
• JSR
308
AnnotaJons
on
Java
Types
Programming
Inheritance
of
Map<@NonNull String, @NonEmpty List<@Readonly Document>> files;!
Behaviour
• JSR
310
Date
and
Time
API
OffsetDateTime now = OffsetDateTime.now();
System.out.println(now.format(DateTimeFormatter.ISO_DATE));!

5. Let’s
Dive
into
Java
8!

6. What
will
change
for
you?
FuncJonal
programming
becomes
mainstream!

7. How
to
get
funcJonal
• Change
the
way
you
look
at
programming
logic:
– Think
in
terms
of
transforming
data
or
input/output
…instead
manipulaJng
state
– Make
immutable
programming
the
default,
mutable
programming
the
excepJon
– FuncJonal
programming
implies
programming
on
a
higher
abstracAon
level

8. How
to
get
funcJonal
• Start
using
higher
order
funcJons
(filter(),
in
CollecJons/Streams
map()
– Whenever
you
use
a
for loop
try
to
come
up
with
a
funcJonal
alternaJve
• Use
Lambda’s
in
your
own
so]ware
structures
– E.g.
Use
Lambda’s
instead
of
a
Template
or
Strategy
pa^ern
• Learn
to
read
Javadoc
for
Lambda’s
etc.)

9. When
to
apply
Virtual
Extension
Methods
• Use
Virtual
Extension
Methods
to
make
new
addiJons
to
your
API
backwards
compaJble
• Add
useful
default
implementaJons
to
your
interfaces
– E.g.
Comparator:
boolean gt(T other), boolean lt(T other)!
• Bundle
cross-­‐cuang
behaviour
in
interfaces
with
default
methods
– E.g.
Logging

10. Q
&
A
Urs
Peter
upeter@xebia.com
@urs_peter