Google Guava & EMF @ GTUG Nantes

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Google
Guava

&

Eclipse
Modeling
Framework
2011/04/26 Mikaël Barbero

Introduction

http://www.ﬂickr.com/photos/drspam/295023450/
1

About me
‣ Modeling consultant
‣ Research engineer
‣ Trainer
‣ Conference Speaker
‣ Language guy ;)

‣ Eclipse committe...

Paris

Nantes

Strategic
members

Acceleo
EMFCompare
ATL
GMF
OCL
Mylyn Intent
EEF Leading
STP

Ava ilable technologies

Guava
Overview

http://www.ﬂickr.com/photos/slowburn/2986303105/
...

http://www.ﬂickr.com/photos/awagnon/1626025855/

About Guava

Java library used Superset of
internally @ Google
Google for years Collections

About Guava

Apache License v2
http://www.apache.org/licenses/LICENSE-2.0

About Guava

s s
ti on ...

Why using Guava?

Simp lexity

http://www.ﬂickr.com/photos/gio_vencato/4941064345/

Why using Guava?

http://www.ﬂickr.com/photos/reway2007/3300379295/

Why using Guava?

Mainstream?

http://www.ﬂickr.com/photos/funtik/1175522045/

Why using Guava?

Helping
others
http://www.ﬂickr.com/photos/thearches/4381959041/

Inside Guava

IO Networking Concurrency

Primitive types Collectio...

Comparison with
Apache Commons
Better ...

B est
rep.

Corest of the
core

http://www.ﬂickr.com/photos/27384147@N02/...

Objects class
public class Person {
final String name, nickname;
final Movie favMovie;

@Override
public boole...

Objects class
public class Person {
final String name, nickname;
final Movie favMovie;
//...

@Override
public ...

Preconditions
Defensive coding

if (state != State.PLAYABLE) {
throw new IllegalStateException(
...

Preconditions
Defensive coding

public void setRating(StarRating rating) {
if (rating == null) {
...

Equivalences strategies
public interface Equivalence<T> {
boolean equivalent(@Nullable T a, @Nullable T b);
int hash(@...

Suppliers
public interface Supplier<T> {
T get();
}

Supplier<String>...

Throwables
Throwables.getCausalChain(throwable);
Throwables.getRootCause(throwable);

Throwables.getStackTraceAsString(thr...

@Annotation

@Beta @VisibleForTesting

@GwtCompatible @GwtIncompatible

Strings

http://www.ﬂickr.com/photos/gernot/2554175292/
4

CharMatcher +1

StringUtil example:
allAscii, collapse, collapseControlChars, collapse...

Getting a CharMatcher
CharMatcher.WHITESPACE (Unicode)
CharMatcher.JAVA_DIGIT
P...

Using your CharMatcher
‣ boolean matchesAllOf(CharSequence)
‣ boolean matchesAny...

Using your CharMatcher
String string = "Scream 4";
CharMatcher matcher = CharMatch...

Splitter +1
JDK has splitter
‣ regular expression
...

Splitter

e_s_jones/5060802981/
...

Splitter
The default behavior is simplistic:
//yields [" foo", " ", "bar", " quux", ""]
...

Ascii, Charsets
Ascii
list of bytes constants for each
Char between 0x00 & 0x7F
Charsets

...

Strings

String str = Strings.emptyToNull(s);

String str = Strings.nullToEmpty(s);

boolean b = Strings.isNullOrEmpty...

CaseFormat
‣ LOWER_CAMEL
‣ Java variable naming convention, e.g., "lowerCamel".

‣ LOWER_HYPHEN
‣ Hy...

Collections

http://www.ﬂickr.com/photos/tochis/1169807846/
5

Ordering

{
Co mparator<T>
pu...

Ordering public class Employee implements Comparable<Employee> {
...

Ordering

Employee anakinSk = new Employee(4, "Anakin Skywalker", 4);
Employee darthVader = new Employee(3, "Dar...

Ordering
Deﬁne your own Comparator
Comparator<Employee> yearsComparator = new Comparator<Employee>() {
@Overr...

Ordering
Create an Ordering from a Comparator
Ordering<Employee> orderUsingYearsCom...

Ordering
toString() ordering

Ordering<Object> toStringOrdering = Ordering.usingToString();

...

What you can do with Ordering

‣ Ordering.min(Iterable<E>)
‣ Ordering.max(Iterable<E>)
‣ Ordering.leastOf(Iterable<E>, int...

What you can do with Ordering

‣ Ordering.sortedCopy(Iterable<E>)
‣ Ordering.immutableSortedCopy(Iterable<E>)

...

Ordering is conﬁgurable
‣ Ordering.reverse()
‣ Ordering.lexicographical()
‣ Ordering.nullsFirst...

ObjectArrays

‣ concat(T, T[])
‣ concat(T[], T)
‣ concat(T[], T[], Class<T>)
‣ newArray(Class<T>, int)
‣ newArray(T[], int)

Multiset & Multimap
Historically, multisets (aka bags) and
multimaps emulated atop maps

Multimap = Map<K, List<V>>...

When to use Multiset?
‣"I kinda want a Set except I can have duplicates"
‣ card games example
‣...

Multiset
Ever done this?
Map<String, Integer> tags = new HashMap<String, Integer>();
for (BlogPo...

Multiset
Would you rather do this?
Multiset<String> tags = HashMultiset.create();
...

Multiset API
‣What if you need to remove/decrement?
‣Don't accidentally go negative
‣Don...

Multiset API

‣int count(Object element);
‣int add(E element, int occurrences);
‣boolean remove(Objec...

Multiset implementations +1

Immut...

When to use Multimap?

Ever done this?
Map<Salesperson, List<Sale>> map = new HashMap<Salesperson,
...

When to use Multimap?
Would you rather do this?

Multimap<Salesperson, Sale> multimap = ArrayListMultimap.create();
...

More about Multimap
A collection of key-value pairs (entries), like a Map,
except that keys don't ...

Multimap subtypes
‣ListMultimap: the get() view implements List
‣preserves the ordering of entries per key;...

Multimap, before
Now we want to ﬁnd the biggest Sale.

Without Multimap:
public Sale getBiggestSale() {
Sale bigge...

$Multimap, after public Sale getBiggestSale() { return Collections.max(multimap.values(), SALE_CHARGE_COMPARATOR); } ...$

Multimap API
Most Map methods are identical on Multimap:
‣ size(),
...

Multimap implementations +1

...

BiMap +1

aka unique-valued map
values are unique, as well as its keys

Has an...

BiMap Implementations

ImmutableBiMap
...

Constrained Collections/Maps

public interface Constraint<E> {
E checkElement(E element);
}

//...
...

Constrained Collections/Maps

Constraints.
constrainedCollection(Collection<E>, Constraint<? super E>)

constrainedLis...

MapMaker +1

A ConcurrentMap builder, providing any combination of
these features:
‣Soft or weak ...

MapMaker

ConcurrentMap<User, Graph> recommendations =
new MapMaker()
.concurrencyLevel(4)
.softKe...

Forwarding Object/Collections

Abstract implementations of existing types
delegating all method calls to its delegate()
...

Forwarding Collections

ForwardingCollection ForwardingMultiset
ForwardingConcurrentMap ForwardingObject
For...

Static utilities
In classes with name ending with an s

‣ Lists
‣ Maps
...

Static factories methods +1
Rather than typing
Map<String, Class<? extends Handler>> m =
...

Maps as index +1

Maps.uniqueIndex()

Map<Integer, Employee> m = Maps.uniqueIndex(values,...

Multimaps as index +1

Multimaps.index()

Multimap<Integer, Employee> m = Multimaps.index...

Map differences +1

So you want to compute the differences
between two maps

...

MapDifference API

Map<K,V> entriesInCommon()
Map<K,V> entriesOnlyOnLeft()
Map<K,V> entriesO...

Sets union/intersection/difference
+1
difference(Set<E>, Set<?>)

symmet...

Sets combinations
Set<Set<E>> powerSet(Set<E>)

while the power set of a set with size n is of size 2^n,
...

Immutable collections

JDK has Collections.unmodiﬁableFoo wrappers

‣Unmodiﬁable - you can't change it
...

Immutable collections +1

Immut...

Immutable collections
JDK wrappers still useful for unmodiﬁable views of
changing data. But for most purpose...

Immutable collections
Factory methods
ImmutableXXX.of() immutable empty XXX
ImmutableXXX.of(E) singletons
Immu...

$Constants Sets public static final Set<Integer> LUCKY_NUMBERS; static { ...$

Constants Sets

public static final Set<Integer> LUCKY_NUMBERS =
Collections
...

Constants Sets
public static final ImmutableSet<Integer> LUCKY_NUMBERS =
ImmutableSet....

$Constants Maps public static final Map<String, Integer> ENGLISH_TO_INT; static { Map<String, Integer> ma...$

Constants Maps

public static final ImmutableMap<String, Integer>
ENGLISH_TO_INT =
...

Table @Beta
since r07
Collection with columns a...

http://www.ﬂickr.com/photos/leamarzloff/3085027173/

Functionnal
...

in com.google.common.base package

public interface Predicate<T> {
Predicate<T> to ﬁ...

in com.google.common.collect package

Iterab...

24 42 13 7 128

public static void demo(Collection<Integer> c) {
Predicate<In...

in com.google.common.collect package

Iterables.transform()
Iterators.transform()
Collections2.transform()
Lists.t...

Apple Orange Banana Kiwi Pear

public void demo(Collection<String> c) {
Functi...

Beware
of

lazyness http://www.ﬂickr.com/photos/torek/2467519466/

Copy!
Lists.newArrayList()
...

Compose and combine
http://www.ﬂickr.com/photos/jgscism/5484243543/

Functions
compose
fo...

Compose and combine
Function<String, String> toUpper = new Function<String, String>() {
@Override
public S...

Compose and combine
Predicate<String> isEmpty = new Predicate<String>() {
@Override
public boolean apply(String inp...

Maps transform & filter
Maps.filterEntries()

Maps.filterKeys()

Maps.filterValues()

Maps.transformEntries()

Maps.transformV...

Primitives

7

common.primitives

package that helps you work with the primitive types
...

common.primitives
Contains the classes
Booleans,
...

The big table
Method Longs Ints Shorts Chars Doubles Bytes S.Bytes ...

http://www.ﬂickr.com/photos/buzzingbye/222969493/

IO & Network

...

common.io 2 key interfaces
...

ByteStreams
‣byte[] toByteArray(InputStream)
‣byte[] toByteArray(InputSupplier)
‣void rea...

Files The Files class works one level higher than
...

More about Files

File createTempDir()
void deleteDirectoryContents(File)
...

Flushab les and Closeables
Flushables.flushQuietly(Flushable flushable)
Flushables.flush(
Flushable fl...

common.net
‣URI
...

Concurrency

http://www.ﬂickr.com/photos/kh-67/3339157498/
9

Concurrency in Guava

Immutable*
...

comm on.util.concurrent
It’s all about Future (as in java.util.concurrent)
...

Future
JDK Future
public interface Future<V> {
...

ListenableFuture

Future with one new method: addListener

When the futur...

ListenableFuture
When to use? Always.

(+) Most Futures methods require it.
(+) It's easier than changin...

Transform and chain

Function<QueryResult, List<Row>> rowsFunction =
new Function<Quer...

Transform and chain

Function<RowKey, ListenableFuture<QueryResult>> queryFunction =
new Function<RowKey, Listenab...

Futures

Got a Iterable<Future<V>>?

Decide what you want:

Future of List<V> ...

Executors

MoreExecutors.sameThreadExecutor
for quick tasks that can r...

Services

"An object with an operational state, plus
asynchronous start() and stop() l...

Services

AbstractExecutionThreadService
One thread automatically created for you at startup

Abstra...

EMF for
dummies

http://www.ﬂickr.com/photos/bendylan/259110679/
...

Java Framework and code generation facility

"Class diagram to Super Java Bean"
(My deﬁnition)

Ab out those modeling things
‣It’s just about deﬁning the entities/concepts/classes
you will manipulate

‣You can deﬁne co...

Ab out those modeling things

‣Thin framework layer inserted into your POJO
‣you can even hide it ;)

‣The layer is as th...

Ab out those modeling things

What can you deﬁne in Ecore ﬁles?

‣Package
‣Classes
‣Attributes
‣Refere...

Ab out those modeling things
‣Packages
Logical organization

‣Classes
Classical OO concepts

‣Attributes
P...

EObject?
The thin layer that changes it all

Object eGet(EStructuralFeature feature);
void eSet(EStructuralFeature ...

time to play

883/
/photos/8728229@N07/4592234
...

EMFPath

http://www.ﬂickr.com/photos/eseartista/1604034788/
11

Path

{
public interface Function<F, T>
Set of functions and }
...

Lazy EObjects containment tree walking

‣ parent (eContainer)

‣ ancestor
‣ ancestorOrSelf
‣ child (eCon...

Common predicates

Having
IsKind/IsType
IsAncestor/IsChild

public static Collection<EObject...

non-EMF functions & predicates
Strings
length : Function<String, Integer>
toL1Case : Function<String, String> ...

Ecore API has been Guava-iﬁed
‣ EObject.eResource() is wrapped as a Function in
EObjectPath.eResource

‣ EObject.eIsProxy(...

Ecore has been Guava-iﬁed through a generator

+

that is available for your own Ecore model

time to play

883/
/photos/8728229@N07/4592234
...

Recap

http://www.ﬂickr.com/photos/loty/326761635/
12

Wha t you should remember
about this presentation

1. Functionnal ﬂavor of collection handling
2. CharMatcher / ...

What you should REALLY remember
about this presentation

1. Guava is cool, powerful and the deﬁnitive
extension to JDK!
...

http://www.ﬂickr.com/photos/wwworks/4759535950/

Q&A