«Новое в JDK 8» BitByte: 20 апреля 2013, Санкт-Петербург http://bitbyte.itmozg.ru/

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Что нового в JDK 8
Александр Ильин
Архитектор тестирования JDK

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The following is intended to outline our general product
direction. It is intended
for information purposes only, and may not be incorporated
into any contract.
It is not a commitment to deliver any material, code, or
functionality, and should not be relied upon in making
purchasing decisions. The development, release, and timing
of any features or functionality described for Oracle’s products
remains at the sole discretion of Oracle.

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Program
Agenda
 50+ изменений
 DateTime API
 Type annotations
 Profiles
 Lambda
http://openjdk.java.net/projects/jdk8/features

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JDK 8
Java for Everyone
• Профайлы
• JSR 310 - Date & Time APIs
• Non-Gregorian calendars
• Unicode 6.1
• ResourceBundle
• BCP47 locale matching
●
Globalization & Accessibility
Innovation
• Lambda (замыкания)
• Language Interop
• Nashorn
Core Libraries
• “Параллельные” коллекции
Improvements in functionality
• Improved type inference
Security
• Ограничение doPrivilege
• NSA Suite B algorithm support
• Поддержка SNI Server Side
• DSA обновление FIPS186-3
• AEAD JSSE CipherSuites
Tools
• Управление компилятором
• JSR 308 – аннотации Java-
типов
• Нативные пакеты
• Инструменты для App Store
Client
●
Новые методы
развертывания
●
JavaFX 8
●
Public UI Control API
●
ПоддержкаEmbedded
●
Поддержка HTML5
●
3D формы и атрибуты
●
Система печати
General Goodness
• Улучшения в JVM
• No PermGen
• Производительность

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Date & Time API: JSR 310

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Instant start = Instant.ofEpochMilli(123450L);
Instant end = Instant.now();
Duration duration = Duration.ofSeconds(12);
Duration bigger = duration.multipliedBy(4);
Duration biggest = bigger.plus(duration);
Instant later = start.plus(duration);
Instant earlier = start.minus(duration);
Date & Time

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LocalDate ld = LocalDate.of(2010, Month.DECEMBER, 3);
LocalDateTime ldt =
LocalDateTime.of(date, LocalTime.of(12, 33));
ZonedDateTime zdt = ZonedDateTime.of(dateTime, zoneId);
zdt = zdt.minus(12, HOURS);
long days = DAYS.between(date1, date2);
Period period = Period.between(date1, date2);
Date & Time

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Type annotations: JSR 308

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Аннотации в Java до Java 8
 @Target
– ANNOTATION_TYPE, CONSTRUCTOR, FIELD,
LOCAL_VARIABLE, METHOD, PACKAGE, PARAMETER, TYPE
 @Retention
– SOURCE, CLASS, RUNTIME
 Поля, значения по умолчанию
– @Test(timeout=100)
– Primitive, String, Class, enum, array of the above
 Нет наследования

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Аннотации в Java 8
 Могут быть использованы на любом использовании типа
– Информация на следующих слайдах ...
 @Target
– TYPE_PARAMETER, TYPE_USE
 Повторяющиеся аннотации
@

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JSR 308: Annotations on Java Types (1)
 method receivers
public int size() @Readonly { ... }
 generic type arguments
Map<@NonNull String, @NonEmpty List<@Readonly Document>>
files;
 arrays
Document[][@Readonly] docs2 =
new Document[2] [@Readonly 12];

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JSR 308: Annotations on Java Types (2)
 typecasts
myString = (@NonNull String)myObject;
 type tests
boolean isNonNull = myString instanceof @NonNull String;
 object creation
new @NonEmpty @Readonly List(myNonEmptyStringSet)

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JSR 308: Annotations on Java Types (3)
 type parameter bounds
<T extends @A Object, U extends @C Cloneable>
 class inheritance
class UnmodifiableList implements @Readonly List<@Readonly T> { ... }
 throws clauses
void monitorTemperature() throws @Critical TemperatureException { ... }

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Nullness checker
Если Nullness checker не рапортует ошибок для какой-либо
программы, тогда во время выполнения этой программы
никогда не будет брошено null pointer exception.
@Nullable Object obj; @NonNull Object nnobj;
...
nnobj.toString(); obj.toString();
nnobj = obj; obj = nnobj;
if (nnobj == null) ...
if (obj != null) {
nnobj = obj; //type refinement
}

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Lock checker
Если Lock checker не рапортует ошибок для какой-либо
программы, тогда программа держит определенный монитор
каждый раз когда доступается до переменной.
 @GuardedBy – доступ разрешен только если держится
определенный монитор
 @Holding – вызов разрешен только если держится определенный
монитор

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Lock checker
@GuardedBy("MyClass.myLock") Object myMethod() { ... }
@GuardedBy("MyClass.myLock") Object x = myMethod();
@GuardedBy("MyClass.myLock") Object y = x;
Object z = x;
x.toString();
synchronized(MyClass.myLock) {
y.toString();
}

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Lock checker
void helper1(@GuardedBy("MyClass.myLock") Object a) {
a.toString();
synchronized(MyClass.myLock) {
a.toString();
}
}
@Holding("MyClass.myLock")
void helper2(@GuardedBy("MyClass.myLock") Object b) {
b.toString();
}

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JDK profiles

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base
tls logging
authjdbc
jtarmi
jaxp
naming
rowset
kerberos management
compiler
xmldsig
prefs
sctp
instrument
scripting
crypto
compat
management.iiop cosnaming
corba
desktop
tools.jre
jaxws
jx.annotations
httpserver
tools
tools.jaxws tools.base
devtools

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base
tls logging
authjdbc
jtarmi
jaxp
naming
rowset
kerberos management
compiler
xmldsig
prefs
sctp
instrument
scripting
crypto
compat
management.iiop cosnaming
corba
desktop
tools.jre
jaxws
jx.annotations
httpserver
tools
tools.jaxws tools.base
devtools
52MB

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base
tls logging
authjdbc
jtarmi
jaxp
naming
rowset
kerberos management
compiler
xmldsig
prefs
sctp
instrument
scripting
crypto
compat
management.iiop cosnaming
corba
desktop
tools.jre
jaxws
jx.annotations
httpserver
tools
tools.jaxws tools.base
devtools
52MB 24

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base
tls logging
authjdbc
jtarmi
jaxp
naming
rowset
kerberos management
compiler
xmldsig
prefs
sctp
instrument
scripting
crypto
compat
management.iiop cosnaming
corba
desktop
tools.jre
jaxws
jx.annotations
httpserver
tools
tools.jaxws tools.base
devtools
52MB 1724

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base
tls logging
authjdbc
jtarmi
jaxp
naming
rowset
kerberos management
compiler
xmldsig
prefs
sctp
instrument
scripting
crypto
compat
management.iiop cosnaming
corba
desktop
tools.jre
jaxws
jx.annotations
httpserver
tools
tools.jaxws tools.base
devtools
1052MB 1724

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Lambda: JSR 335

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Lambda
 Лямбда
(Object o) -> (o.toString());
 Ссылка на метод
Object::toString()
 Метод по умолчанию
Collection.forEach(java.util.function.Block)
 Collections
shapes.stream().filter(s s.getColor() == BLUE).
map(s s.getWeight()).sum();

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Функциональные интерфейсы
Интерфейс с одним методом
●
Runnable, Comparator, ActionListener
●
Predicate<T>, Block<T>
Лямбда - экземпляр функционального интерфейса
Predicate<String> isEmpty = s s.isEmpty();
Predicate<String> isEmpty = String::isEmpty;
Runnable r = () {System.out.println(“Boo!”) };

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Эволюция интерфейсов
 Палка о двух концах
– Гибкость
• Специфицирован только API
– Невозможно изменить
• Требуется менять все имплементации

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Методы по умолчанию
interface Collection<E> {
default void forEach(Block<E> action) {
for (E e: this) action.apply(e);
}
default boolean removeIf(Predicate<? super E> filter) {
boolean removed = false; Iterator<E> each = iterator();
while ( each.hasNext() ) {
if ( filter.test( each.next() ) ) {
each.remove(); removed = true;
}
}
return removed;
}
}

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Методы по умолчанию
Множественное наследование?
 Интерфейса
 Поведения
 Состояния

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Методы по умолчанию
Множественное наследование?
 Интерфейса
 Поведения
 Состояния
было всегда

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Методы по умолчанию
Множественное наследование?
 Интерфейса
 Поведения
 Состояния
было всегдабыло всегда
методы по умолчанию

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Методы по умолчанию
Множественное наследование?
 Интерфейса
 Поведения
 Состояния
методы по умолчанию
было всегда

34. Copyright © 2012, Oracle and/or its affiliates. All rights reserved.34
Методы по умолчанию
Множественное наследование?
1.Класс побеждает
2.Более специфичный интерфейс предпочтительней
3.Во всех остальных случаях пользователь должен предоставить
реализацию
 Интерфейса
 Поведения
 Состояния
было всегда
методы по умолчанию

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Diamonds? Нет проблем!
interface A {
default void m() {…}
}
interface B extends A {…}
interface C extends A {…}
class D implements B, C {...}
A
B C
D
m

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Diamonds? Нет проблем!
interface A {
default void m() {…}
}
interface B extends A {
default void m() {…}
}
interface C extends A {...}
сlass D implements B, C {...}
A
B C
D
m
m

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Явное разрешение неоднозначности
interface A {
default void m() {…}
}
interface B {
default void m() {…}
}
class C implements A, B {
//Must implement/reabstract m()
void m() { A.super.m(); }
}
A B
D
m m

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Cортировка
Collections.sort(people, new Comparator<Person>() {
public int compare(Person x, Person y) {
return x.getLastName().compareTo(y.getLastName());
}
});

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Сортировка с лямбдой
Comparator<Person> byLastName
= comparing(p p.getLastName());
Collections.sort(people, byLastName);
Collections.sort(people, comparing(p
p.getLastName()));
people.sort(comparing(p p.getLastName()))

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Сортировка с лямбдой
people.sort(comparing(Person::getLastName))
people.sort(comparing(Person::getLastName).reverse());
people.sort(comparing(Person::getLastName)
.compose(comparing(Person::getFirstName)));

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Что нового в JDK 8
Александр Ильин
Архитектор тестирования JDK