3. About me
‣ Modeling consultant
‣ Research engineer
‣ Trainer
‣ Conference Speaker
‣ Language guy ;)
‣ Eclipse committer
‣ Guava-OSGi packager
‣ EMFPath lead
16. About Guava
Apache License v2
http://www.apache.org/licenses/LICENSE-2.0
17. About Guava
s s
ti on ti on
c
lle llec
Co 5 Co a r03 a r08
gle v0. gle v1 uav uav
G oo G oo G G
2007 2008 2009 2010 2011
Frequent releases (quarterly base)
Latest release (r09): April, 7th
24. Inside Guava
IO Networking Concurrency
Primitive types Collections
GWT compatibility is tested (see @GwtCompatible)
25. Comparison with
Apache Commons
Better Better
More Modern
Designed Supported
Best practices Actively
Java 5 developed
and patterns (- commons 3.0)
Respects JDK Google
Orthogonality
contracts (@Beta to test designs) depends on it
(e.g., Google Guice)
http://stackoverflow.com/questions/4542550/what-are-the-big-improvements-between-guava-and-apache-equivalent-libraries
27. Corest of the
core
http://www.flickr.com/photos/27384147@N02/5211738745/
3
28. Objects class
public class Person {
final String name, nickname;
final Movie favMovie;
@Override
public boolean equals(Object object) {
if (object instanceof Person) {
Person that = (Person) object;
return Objects.equal(this.name, that.name)
&& Objects.equal(this.nickname, that.nickname)
&& Objects.equal(this.favMovie, that.favMovie);
}
return false;
}
@Override
public int hashCode() {
return Objects.hashCode(name, nickname, favMovie);
}
}
Example from http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
29. Objects class
public class Person {
final String name, nickname;
final Movie favMovie;
//...
@Override
public String toString() {
return Objects.toStringHelper(this)
.add("name", name)
.add("nickname", nickname)
.add("favMovie", favMovie)
.toString();
}
public String preferredName() {
return Objects.firstNonNull(nickname, name);
}
}
Example from http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
30. Preconditions
Defensive coding
if (state != State.PLAYABLE) {
throw new IllegalStateException(
"Can't play movie; state is " + state);
}
Preconditions.checkState(state == State.PLAYABLE,
"Can't play movie; state is %s", state);
Example from http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
31. Preconditions
Defensive coding
public void setRating(StarRating rating) {
if (rating == null) {
throw new NullPointerException();
}
this.rating = rating;
}
public void setRating(StarRating rating) {
this.rating = checkNotNull(rating);
}
Example from http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
32. Equivalences strategies
public interface Equivalence<T> {
boolean equivalent(@Nullable T a, @Nullable T b);
int hash(@Nullable T t);
}
Equivalence equals = Equivalences.equals();
Equivalence identity = Equivalences.identity();
Equivalence<String> elementEquivalence = ...;
Equivalence<Iterable<String>> pairwise =
Equivalences.pairwise(elementEquivalence);
Collection<String> c1, c2;
pairwise.equivalent(c1, c2);
33. Suppliers
public interface Supplier<T> {
T get();
}
Supplier<String> s = ...;
Supplier<String> memoizing = Suppliers.memoize(s);
Supplier<String> expiring =
Suppliers.memoizeWithExpiration(s, 100, TimeUnit.SECONDS);
Supplier<String> ofInstance =
Suppliers.ofInstance("Always returning");
37. CharMatcher +1
StringUtil example:
allAscii, collapse, collapseControlChars, collapseWhitespace, indexOfChars, lastIndexNotOf,
numSharedChars, removeChars, removeCrLf, replaceChars, retainAllChars, strip,
stripAndCollapse, stripNonDigits, ...
Partial cross product of two notions:
(a) what's a "matching" character?
(b) what to do with those matching characters?
CharMatcher:
An instance of this type represents part (a),
and the operation you invoke on it represents part (b).
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
38. Getting a CharMatcher
CharMatcher.WHITESPACE (Unicode)
CharMatcher.JAVA_DIGIT
Predefined constants
CharMatcher.ASCII
(examples)
CharMatcher.ANY
Factory methods
CharMatcher.is('x') (examples)
CharMatcher.isNot('_')
CharMatcher.oneOf("aeiou").negate()
CharMatcher.inRange('a', 'z').or(inRange('A', 'Z'))
Subclass CharMatcher, implement matches(char c)
Now check out all that you can do...
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
40. Using your CharMatcher
String string = "Scream 4";
CharMatcher matcher = CharMatcher.JAVA_LETTER_OR_DIGIT;
int count = matcher.countIn(string);
System.out.println("Letter or digit count: "+count);
// Letter or digit count: 7
System.out.println(matcher.matchesAllOf("scream"));
// true
System.out.println(matcher.matchesAllOf("scream "));
// false
System.out.println(matcher.matchesNoneOf("_?=)("));
// true
http://scaramoche.blogspot.com/2010/05/googles-guava-library-tutorial-part-1.html
41. Splitter +1
JDK has splitter
‣ regular expression
‣ result as an array
‣ its way of handling empty pieces (which is very strange)
Mini-puzzler
",a,,b,".split(",") returns...
(a) "", "a", "", "b", ""
(b) null, "a", null, "b", null
(c) "a", null, "b"
(d) "a", "b"
(e) None of the above
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
42. Splitter
e_s_jones/5060802981/
http://www.flickr.com/photos/terenc
Splitter is String.split() on steroids
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
43. Splitter
The default behavior is simplistic:
//yields [" foo", " ", "bar", " quux", ""]
Splitter.on(',').split(" foo, ,bar, quux,");
If you want extra features, ask for them!
//yields ["foo", "bar", "quux"]
Splitter.on(',')
.trimResults()
.omitEmptyStrings()
.split(" foo, ,bar, quux,");
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
44. Ascii, Charsets
Ascii
list of bytes constants for each
Char between 0x00 & 0x7F
Charsets
by
G uaranteed to be supported
ons
al l Java platform implementati
No more
‣Charsets.ISO_8859_1; try {
bytes = string.getBytes("UTF-8");
‣Charsets.US_ASCII; } catch (UnsupportedEncodingException e) {
‣Charsets.UTF_16; // how can this possibly happen?
‣Charsets.UTF_16BE; throw new AssertionError(e);
}
‣Charsets.UTF_16LE;
‣Charsets.UTF_8;
48. Ordering
{
Co mparator<T>
publ ic interface );
int compare(T, T
abstract equals(Objec
t);
ean
a bstract bool
}
Comparator is easy to implement, but a pain to use
Push the Comparator<T> interface to the next level
http://scaramoche.blogspot.com/2010/05/googles-guava-library-tutorial-part-2.html
49. Ordering public class Employee implements Comparable<Employee> {
private final int id;
private final String name;
private final int yearsOfService;
public Employee(int id, String name, int yearsOfService) {
this.id = id;
this.name = name;
this.yearsOfService = yearsOfService;
}
Simple
public int getId() { return id; }
public String getName() { return name; }
data class public int getYearsOfService() { return yearsOfService; }
@Override
public int compareTo(Employee employee) {
return this.getName().compareTo(employee.getName());
}
@Override
public String toString() {
return Objects.toStringHelper(this)
.add("id", id)
.add("name", name)
.add("years of service", yearsOfService)
.toString();
}
}
http://scaramoche.blogspot.com/2010/05/googles-guava-library-tutorial-part-2.html
50. Ordering
Employee anakinSk = new Employee(4, "Anakin Skywalker", 4);
Employee darthVader = new Employee(3, "Darth Vader", 5);
Employee hanSolo = new Employee(2, "Han Solo", 10);
List <Employee> employeeList =
Lists.newArrayList(anakinSk, hanSolo, darthVader);
System.out.println("employee list: "+employeeList);
employee list: [Employee{id=4, name=Anakin
Skywalker, years of service=4}, Employee{id=2,
name=Han Solo, years of service=10}, Employee
{id=3, name=Darth Vader, years of service=5}]
http://scaramoche.blogspot.com/2010/05/googles-guava-library-tutorial-part-2.html
51. Ordering
Define your own Comparator
Comparator<Employee> yearsComparator = new Comparator<Employee>() {
@Override
public int compare(Employee employee1, Employee employee2) {
return (employee1.getYearsOfService() - employee2
.getYearsOfService());
}
};
Comparator<Employee> idComparator = new Comparator<Employee>() {
@Override
public int compare(Employee employee1, Employee employee2) {
return (employee1.getId() - employee2.getId());
}
};
http://scaramoche.blogspot.com/2010/05/googles-guava-library-tutorial-part-2.html
52. Ordering
Create an Ordering from a Comparator
Ordering<Employee> orderUsingYearsComparator =
Ordering.from(yearsComparator);
Use your ordering, e.g. to sort
List<Employee> sortedCopy =
orderUsingYearsComparator.sortedCopy(employeeList);
System.out.println("sorted copy: " + sortedCopy);
sorted copy: [Employee{id=4, name=Anakin Skywalker,
years of service=4}, Employee{id=3, name=Darth Vader,
years of service=5}, Employee{id=2, name=Han Solo,
years of service=10}]
http://scaramoche.blogspot.com/2010/05/googles-guava-library-tutorial-part-2.html
54. What you can do with Ordering
‣ Ordering.min(Iterable<E>)
‣ Ordering.max(Iterable<E>)
‣ Ordering.leastOf(Iterable<E>, int)
‣ Ordering.greatestOf(Iterable<E>, int)
‣ Ordering.isOrdered(Iterable<? extends T>)
‣ Ordering.isStrictlyOrdered(Iterable<? extends T>)
‣ Ordering.binarySearch(List<? extends T>, T)
55. What you can do with Ordering
‣ Ordering.sortedCopy(Iterable<E>)
‣ Ordering.immutableSortedCopy(Iterable<E>)
new TreeSet( Collection)
Better than
card duplicate s elements
Do not dis
Performed sort is stable
56. Ordering is configurable
‣ Ordering.reverse()
‣ Ordering.lexicographical()
‣ Ordering.nullsFirst()
‣ Ordering.nullsLast()
‣ Ordering.reverse()
Lexicographical returns an
Ordering on Iterable of T
[] < [1] < [1, 1] < [1, 2] < [2]
59. When to use Multiset?
‣"I kinda want a Set except I can have duplicates"
‣ card games example
‣ changing to List sacrifices contains() performance
‣"Are these Lists equal, ignoring order?"
‣ write a utility method for this? Histograms
‣"What distinct tags am I using on my blog, and how
many times do I use each one?"
Multiset performance varies by the number
of distinct elements, not total size.
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
60. Multiset
Ever done this?
Map<String, Integer> tags = new HashMap<String, Integer>();
for (BlogPost post : getAllBlogPosts()) {
for (String tag : post.getTags()) {
int value = tags.containsKey(tag) ? tags.get(tag) : 0;
tags.put(tag, value + 1);
}
}
distinct tags:
tags.keySet()
count for "java" tag:
Usage tags.containsKey("java") ? tags.get("java") : 0;
total count:
// oh crap...
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
61. Multiset
Would you rather do this?
Multiset<String> tags = HashMultiset.create();
for (BlogPost post : getAllBlogPosts()) {
tags.addAll(post.getTags());
}
distinct tags:
tags.elementSet();
Usage count for "java" tag:
tags.count("java");
(hurrah)
total count:
tags.size();
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
62. Multiset API
‣What if you need to remove/decrement?
‣Don't accidentally go negative
‣Don't forget to prune!
‣(Or just use a Multiset.)
‣What about concurrency?
‣Lock the entire map just to add one tag?
‣(Or just use our ConcurrentMultiset.)
When you use a powerful library, your
code can easily evolve.
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
63. Multiset API
‣int count(Object element);
‣int add(E element, int occurrences);
‣boolean remove(Object element, int occurrences);
‣int setCount(E element, int newCount);
‣boolean setCount(E e, int oldCount, int newCount);
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
65. When to use Multimap?
Ever done this?
Map<Salesperson, List<Sale>> map = new HashMap<Salesperson,
List<Sale>>();
public void makeSale(Salesperson salesPerson, Sale sale) {
List<Sale> sales = map.get(salesPerson);
if (sales == null) {
sales = new ArrayList<Sale>();
map.put(salesPerson, sales);
}
sales.add(sale);
}
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
66. When to use Multimap?
Would you rather do this?
Multimap<Salesperson, Sale> multimap = ArrayListMultimap.create();
public void makeSale(Salesperson salesPerson, Sale sale) {
multimap.put(salesPerson, sale);
}
The code on the previous slide is
‣Verbose
‣Bug-prone
‣Limited in functionality
‣Using the wrong abstraction
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
67. More about Multimap
A collection of key-value pairs (entries), like a Map,
except that keys don't have to be unique.
{a=1, a=2, b=3, c=4, c=5, c=6}
multimap.get(key) returns a modifiable Collection view
of the values associated with that key.
Sometimes you want to think of it as a Map<K,
Collection<V>> -- use the asMap() view:
{a=[1, 2], b=[3], c=[4, 5, 6]}
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
68. Multimap subtypes
‣ListMultimap: the get() view implements List
‣preserves the ordering of entries per key;
‣can have duplicate entries
‣SetMultimap: the get() view implements Set
‣no duplicate entries,
‣ordering of entries is impl-dependent
‣SortedSetMultimap: the get() view implements SortedSet
‣you get the idea
Hmm... sounds a lot like a plain old Map<K, Collection<V>>?
But wait...
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
69. Multimap, before
Now we want to find the biggest Sale.
Without Multimap:
public Sale getBiggestSale() {
Sale biggestSale = null;
for (List<Sale> sales : map.values()) {
Sale myBiggestSale = Collections.max(
sales,
SALE_CHARGE_COMPARATOR);
if (biggestSale == null
|| myBiggestSale.getCharge() > biggestSale().getCharge()) {
biggestSale = myBiggestSale;
}
}
return biggestSale;
}
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
70. Multimap, after
public Sale getBiggestSale() {
return Collections.max(multimap.values(), SALE_CHARGE_COMPARATOR);
}
View collections are very powerful.
Multimap has six:
‣get(),
‣keys(),
‣keySet(),
‣values(),
‣entries(),
‣asMap().
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
71. Multimap API
Most Map methods are identical on Multimap:
‣ size(),
‣ isEmpty(),
‣ containsKey(),
‣ containsValue(),
‣ put(),
‣ putAll(),
‣ clear(),
‣ values()
The others have analogues:
‣ get() returns Collection<V> instead of V
‣ remove(K) becomes remove(K,V) and removeAll(K)
‣ keySet() becomes keys() (well, and keySet())
‣ entrySet() becomes entries()
And Multimap has a few new things:
‣ containsEntry(),
‣ replaceValues()
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
73. BiMap +1
aka unique-valued map
values are unique, as well as its keys
Has an inverse() view, which is another BiMap
bimap.inverse().inverse() == bimap
Stop creating two separate
forward and backward Maps!
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
75. Constrained Collections/Maps
public interface Constraint<E> {
E checkElement(E element);
}
//...
public Object checkElement(Object element) {
if (element == null) {
throw new NullPointerException();
}
return element;
} Constraints.n
otNull()
//...
76. Constrained Collections/Maps
Constraints.
constrainedCollection(Collection<E>, Constraint<? super E>)
constrainedList(List<E>, Constraint<? super E>)
constrainedMultiset(Multiset<E>, Constraint<? super E>)
constrainedSet(Set<E>, Constraint<? super E>)
constrainedSortedSet(SortedSet<E>, Constraint<? super E>)
77. MapMaker +1
A ConcurrentMap builder, providing any combination of
these features:
‣Soft or weak keys
‣Soft or weak values
‣Timed expiration
‣On-demand computation of values
Far more powerful, easy to use than WeakHashMap
Concurrent on-demand computation is really hard
78. MapMaker
ConcurrentMap<User, Graph> recommendations =
new MapMaker()
.concurrencyLevel(4)
.softKeys()
.weakValues()
.maximumSize(10000)
.expireAfterWrite(10, TimeUnit.MINUTES)
.makeComputingMap(
new Function<User, Graph>() {
public Graph apply(User user) {
return createExpensiveGraph(user);
}
});
79. Forwarding Object/Collections
Abstract implementations of existing types
delegating all method calls to its delegate()
protected abstract Object delegate();
Decorator pattern without the burden ;)
81. Static utilities
In classes with name ending with an s
‣ Lists
‣ Maps
‣ Multimaps
‣ Multisets
‣ Sets
‣ SortedMaps
‣ Tables
‣ Iterators
‣ Iterables
‣ Collections2
82. Static factories methods +1
Rather than typing
Map<String, Class<? extends Handler>> m =
new HashMap<String, Class<? extends Handler>>();
you type
Map<String, Class<? extends Handler>> m2 = Maps.newHashMap();
Guava provides these for JDK collections
and for Guava collections (Multi*...)
With overloads to accept Iterables to
copy elements from
83. Maps as index +1
Maps.uniqueIndex()
Map<Integer, Employee> m = Maps.uniqueIndex(values,
new Function<Employee, Integer>() {
@Override
public Integer apply(Employee input) {
return input.getId();
}
});
84. Multimaps as index +1
Multimaps.index()
Multimap<Integer, Employee> m = Multimaps.index(values,
new Function<Employee, Integer>() {
@Override
public Integer apply(Employee input) {
return input.getYearsOfService();
}
});
85. Map differences +1
So you want to compute the differences
between two maps
Guava has it too
Maps.difference(
Map<? extends K,? extends V>,
Map<? extends K,? extends V>)
Difference is an immutable snapshot of the state of the
maps at the time this method is called
86. MapDifference API
Map<K,V> entriesInCommon()
Map<K,V> entriesOnlyOnLeft()
Map<K,V> entriesOnlyOnRight()
Map<K,MapDifference.ValueDifference<V>> entriesDiffering()
ValueDifference API
V leftValue()
V rightValue()
88. Sets combinations
Set<Set<E>> powerSet(Set<E>)
while the power set of a set with size n is of size 2^n,
its memory usage is only O(n)
Set<List<B>> cartesianProduct(
List<? extends Set<? extends B>>)
while the cartesian product of sets of size m, n, p
is a set of size m x n x p, its actual memory
consumption is much smaller (m + n + p)
89. Immutable collections
JDK has Collections.unmodifiableFoo wrappers
‣Unmodifiable - you can't change it
‣Immutable - it can never change, no matter what
‣Immutability is tasty!
‣See Effective Java Item 15 for some of the many reasons
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
91. Immutable collections
JDK wrappers still useful for unmodifiable views of
changing data. But for most purposes, use Guava’s:
‣Brand-new, standalone implementations
‣Immutability guaranteed!
‣Very easy to use
‣See following slides
‣Slightly faster
‣Null hostile
‣Use less memory
‣Sometimes far less (ImmutableSet, factor of 2-3x)
http://google-collections.googlecode.com/files/google-collections-svgtug-2008-08-06.pdf
92. Immutable collections
Factory methods
ImmutableXXX.of() immutable empty XXX
ImmutableXXX.of(E) singletons
ImmutableXXX.of(E, E)
ImmutableXXX.of(E, E, E, E...)
ImmutableXXX.copyOf(Iterable)
ImmutableXXX.copyOf(Iterator)
small maps only (up
ImmutableMap.of(1, "one", 2, "two") to 5 key/value pairs)
ImmutableMap.copyOf(Map)
Builder pattern otherwise
93. Constants Sets
public static final Set<Integer> LUCKY_NUMBERS;
static {
Set<Integer> set = new LinkedHashSet<Integer>();
set.add(4);
set.add(8);
set.add(15);
set.add(16);
set.add(23);
set.add(42);
LUCKY_NUMBERS = Collections.unmodifiableSet(set);
}
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
94. Constants Sets
public static final Set<Integer> LUCKY_NUMBERS =
Collections
.unmodifiableSet(
new LinkedHashSet<Integer>(
Arrays.asList(4, 8, 15, 16, 23, 42)));
A little nicer. But uses four different classes!
Something's weird.
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
95. Constants Sets
public static final ImmutableSet<Integer> LUCKY_NUMBERS =
ImmutableSet.of(4, 8, 15, 16, 23, 42);
Now we just say exactly what we mean.
And get performance benefits as well!
We're using just one class (it implements Set)
of() method name inspired by java.util.EnumSet
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
100. in com.google.common.base package
public interface Predicate<T> {
Predicate<T> to filter boolean apply(T from);
out a collection }
{
public interface Function<F, T>
T apply(F from);
Function<F, T> to
} transform a collection
101. in com.google.common.collect package
Iterables.filter()
Iterators.filter()
Collections2.filter()
Sets.filter()
http://www.flickr.com/photos/luis_is_rubbish_at_photography/5464233571/
106. Copy!
Lists.newArrayList()
Lists.newLinkedList()
Sets.newHashSet()
Sets.newLinkedHashSet()
Sets.newTreeSet()
or make it immutable...
ImmutableList.copyOf()
ImmutableSet.copyOf()
http://www.flickr.com/photos/visionnewspaper/314107094/
107. Compose and combine
http://www.flickr.com/photos/jgscism/5484243543/
Functions
compose
forPredicate
Predicates
and
or
not
compose
108. Compose and combine
Function<String, String> toUpper = new Function<String, String>() {
@Override
public String apply(String input) {
return input.toUpperCase();
}
};
Function<Integer, String> toHexString = new Function<Integer, String>() {
@Override
public String apply(Integer input) {
return Integer.toHexString(input.intValue());
}
};
Function<Integer, String> toUpperHexString =
Functions.compose(toUpper, toHexString);
109. Compose and combine
Predicate<String> isEmpty = new Predicate<String>() {
@Override
public boolean apply(String input) {
return input.length() == 0; // isEmpty() is Java6 only
}
};
Predicate<Object> isNull = new Predicate<Object>() {
@Override
public boolean apply(Object input) {
return input == null;
}
};
Predicate<String> nullOfEmpty = Predicates.or(isNull, isEmpty);
112. common.primitives
package that helps you work with the primitive types
int, long, double, float, char, byte, short, and boolean
If you need help doing a primitive task:
1. check the wrapper class (e.g. java.lang.Integer)
2. check java.util.Arrays
3. check com.google.common.primitives
4. it might not exist!
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
113. common.primitives
Contains the classes
Booleans,
Each has the exact same structure
Bytes, (but has only the subset of operations that make sense for its type).
Chars,
Doubles,
Floats, Many of the byte-related methods
Ints, have alternate versions in the classes
Longs and (wait for it) SignedBytes and UnsignedBytes.
(Bytes are peculiar...)
Shorts
Guava doesn't do primitive-based collections; try fastutil, or trove4j, or...
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
114. The big table
Method Longs Ints Shorts Chars Doubles Bytes S.Bytes U.Bytes Booleans
hashCode x x x x x x x
compare x x x x x x x x
checkedCast x x x x x
saturadCast x x x x x
contains x x x x x x
indexOf x x x x x x x
lastIndexOf x x x x x x x
min x x x x x x
max x x x x x x
concat x x x x x x x
join x x x x x x x
toArray x x x x x x x
asList x x x x x x x
lexComparator x x x x x x x
toByteArray x x x x
fromByteArray x x x x
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
116. common.io 2 key interfaces
public interface InputSupplier<T> {
T getInput() throws IOException;
}
Typically:
public interface OutputSupplier<T> {
InputSupplier<InputStream>,
OutputSupplier<Writer>, etc. T getOutput() throws IOException;
}
This lets all Guava’s utilities be useful for many kinds of I/O.
Terminology
‣ byte stream means "InputStream or OutputStream"
ByteStreams utilities class
‣ char stream means "Reader or Writer."
CharStreams utilities class
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
117. ByteStreams
‣byte[] toByteArray(InputStream)
‣byte[] toByteArray(InputSupplier)
‣void readFully(InputStream, byte[])
‣void write(byte[], OutputSupplier)
‣long copy(InputStream, OutputStream)
‣long copy(InputSupplier, OutputSupplier)
‣long length(InputSupplier)
‣boolean equal(InputSupplier, InputSupplier)
‣InputSupplier slice(InputSupplier, long, long)
‣InputSupplier join(InputSupplier...)
CharStreams is similar, but deals in Reader, Writer, String and
CharSequence (often requiring you to specify a Charset).
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
118. Files The Files class works one level higher than
ByteStreams and CharStreams
byte[] toByteArray(File)
void write(byte[], File)
void write(CharSequence, File, Charset)
long copy(File, File)
long copy(InputSupplier, File)
long copy(File, OutputSupplier)
long copy(File, Charset, Appendable)
long move(File, File)
boolean equal(File, File)
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
119. More about Files
File createTempDir()
void deleteDirectoryContents(File)
void deleteRecursively(File)
long getChecksum(File, Checksum)
byte[] getDigest(File, MessageDigest)
String readFirstLine(File, Charset)
List<String> readLines(File, Charset)
T readLines(File, Charset, LineProcessor<T>)
String toString(File, Charset)
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
120. Flushab les and Closeables
Flushables.flushQuietly(Flushable flushable)
Flushables.flush(
Flushable flushable,
boolean swallowIOException) throws IOException
Closeables.closeQuietly(Closeable closeable)
Closeables.close(
Closeable closeable,
boolean swallowIOException) throws IOException
Very usefull in finally blocks
(avoid nesting try/catch)
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
121. common.net
‣URI
Work with literals of: ‣URL
‣@IP (v4/v6)
Never cause DNS services to
be accessed
(JDK does...)
HostSpecifier
syntactically valid host specifier, suitable for use in a URI
InternetDomainName
~RFC 1035, i18n DN
InetAddresses
utility pertaining to Inet(4|6)Address instances
http://guava-libraries.googlecode.com/files/Guava_for_Netflix_.pdf
123. Concurrency in Guava
Immutable*
ConcurrentHashMultiset
Multimaps.synchronizedMultimap
MapMaker
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
124. comm on.util.concurrent
It’s all about Future (as in java.util.concurrent)
(never heard of it, go take a nap)
"A handle to an in-progress computation."
"A promise from a service to supply us with a result."
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
125. Future
JDK Future
public interface Future<V> {
//...
V get();
//...
}
Guava ListenableFuture
public interface ListenableFuture<V> extends Future<V> {
void addListener(Runnable r, Executor e);
}
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
126. ListenableFuture
Future with one new method: addListener
When the future is done (success, exception,
cancellation), the listeners run
the killer app: "To serve as a foundation for higher-
level abstractions"
See Futures
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
127. ListenableFuture
When to use? Always.
(+) Most Futures methods require it.
(+) It's easier than changing to ListenableFuture later.
(+) Providers of utility methods won't need to provide
Future and ListenableFuture variants of their methods.
(−) "ListenableFuture" is lengthier than "Future."
(−) Classes like ExecutorService give you a plain
Future by default.
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
130. Futures
Got a Iterable<Future<V>>?
Decide what you want:
Future of List<V> Futures.allAsList()
List of Future<V> Futures.successfulAsList()
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
131. Executors
MoreExecutors.sameThreadExecutor
for quick tasks that can run inline
MoreExecutors.getExitingExecutorService
for "half-daemon" threads
UncaughtExceptionHandlers.systemExit
for exiting after unexpected errors
ThreadFactoryBuilder
new ThreadFactoryBuilder()
.setDaemon(true)
.setNameFormat("WebRequestHandler-%d")
.build();
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
132. Services
"An object with an operational state, plus
asynchronous start() and stop() lifecycle methods
to transfer into and out of this state."
Example: web servers, RPC servers, monitoring initialization, ...
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
133. Services
AbstractExecutionThreadService
One thread automatically created for you at startup
AbstractIdleService
Thread only needed for startup and shutdown (e.g., service
that already has its own thread)
AbstractService
Full control over threads creation
http://guava-libraries.googlecode.com/files/guava-concurrent-slides.pdf
134. EMF for
dummies
http://www.flickr.com/photos/bendylan/259110679/
10
135. Java Framework and code generation facility
"Class diagram to Super Java Bean"
(My definition)
136. Ab out those modeling things
‣It’s just about defining the entities/concepts/classes
you will manipulate
‣You can define concepts in several ways
‣Annotated Java classes
‣XML Schema
‣Ecore file
‣UML Class diagram
‣You give the input to EMF, and it handles conversion
and generation of the ULTIMATE POJO API
137. Ab out those modeling things
‣Thin framework layer inserted into your POJO
‣you can even hide it ;)
‣The layer is as thin as imaginable and provides high
power-to-weight ratio
‣opposite references
‣adapters
‣edit
‣lazy loading
‣serialization (REST)
‣factory
‣reflective calls / metadata generation
138. Ab out those modeling things
What can you define in Ecore files?
‣Package
‣Classes
‣Attributes
‣References
139. Ab out those modeling things
‣Packages
Logical organization
‣Classes
Classical OO concepts
‣Attributes
Primitive type fields (with cardinality)
‣References
Class type fields (with cardinality), opposite,
containment
140. EObject?
The thin layer that changes it all
Object eGet(EStructuralFeature feature);
void eSet(EStructuralFeature feature, Object newValue);
boolean eIsSet(EStructuralFeature feature);
void eUnset(EStructuralFeature feature);
EList<EObject> eContents();
TreeIterator<EObject> eAllContents();
EObject eContainer();
141. time to play
883/
/photos/8728229@N07/4592234
http://www.flickr.com
http://www.flickr.com/photos/squonk
/1715142327/
144. {
public interface Function<F, T>
Set of functions and }
T apply(F from);
public interface Predicate<T> {
predicates for EMF objects }
boolean apply(T from);
Code generators for your
own Ecore models
and few other utility classes
146. Common predicates
Having
IsKind/IsType
IsAncestor/IsChild
public static Collection<EObject> demoHaving(Collection<EObject> c) {
return Collections2.filter(c,
Having.feature(EcorePackage.Literals.ENAMED_ELEMENT__NAME,
StringPredicates.firstUpperCase)
);
}
147. non-EMF functions & predicates
Strings
length : Function<String, Integer>
toL1Case : Function<String, String> Comparable
toLowerCase : Function<String, String>
toU1Case : Function<String, String> Predicates to
toUpperCase : Function<String, String> test ordering:
trim : Function<String, String> equal
replaceAll(Pattern, String) less than
replaceAll(String, String) greater than
replaceFirst(Pattern, String) less or equal
replaceFirst(String, String) greater or equal
substring(int)
substring(int, int)
148. Ecore API has been Guava-ified
‣ EObject.eResource() is wrapped as a Function in
EObjectPath.eResource
‣ EObject.eIsProxy() is wrapped as a Predicate in
EObjectPath.eIsProxy
‣ EClass.getESuperTypes() is wrapped as a
Function in EClass.eSuperTypes
‣ EReference.isContainment() is wrapped as a
Predicate in ERefrencePath.isContainment
149. Ecore has been Guava-ified through a generator
+
that is available for your own Ecore model
150. time to play
883/
/photos/8728229@N07/4592234
http://www.flickr.com
http://www.flickr.com/photos/squonk
/1715142327/
152. Wha t you should remember
about this presentation
1. Functionnal flavor of collection handling
2. CharMatcher / Splitter / Joiner
3. Immutable Collections
4. Multimap / Multiset / Bimap
5. MapMaker
6. EMF is generating plain old POJO
153. What you should REALLY remember
about this presentation
1. Guava is cool, powerful and the definitive
extension to JDK!
2. Never write your own POJO by hand for
now, use EMF!
3. Always generate EMFPath classes to
handle EMF objects!
http://code.google.com/p/guava-libraries/
http://code.google.com/p/guava-osgi/
http://eclipse.org/modeling/emf/
http://code.google.com/a/eclipselabs.org/p/emfpath/
