OpenJDK for a’N’droidlingsMurat Yener

@yenerm

who am I?Java, Web, Android

Android @Intel

Speaker (Devoxx, JavaOne, DroidCon..)

GDG Organizer

Book Author (Java EE DP, Android Studio)

GDE on Android & Java Champion

what the JDK?

Android is Java

but.. not on JRE

based on Apache Harmony

Object.java Object.class classes.dx

Java7? Java8?

but Harmony is Java 6??

Java 7 introduces changes to JVM! (JSR-292)

Java 8 introduces language features based on…

Java 8 Language FeaturesDefault and Static Interface methods

Lambda Expressions

Repeatable Annotations

Method References

Type Annotations

https://developer.android.com/guide/platform/j8-jack.html

Default Methodspublic interface TimeClient { void setTime(int hour, int minute, int second); void setDate(int day, int month, int year); void setDateAndTime(int day, int month, int year, int hour, int minute, int second); LocalDateTime getLocalDateTime(); static ZoneId getZoneId (String zoneString) { try { return ZoneId.of(zoneString); } catch (DateTimeException e) { return ZoneId.systemDefault(); } } default ZonedDateTime getZonedDateTime(String zoneString) { return ZonedDateTime.of(getLocalDateTime(), getZoneId(zoneString)); } }

Default Methodspublic interface TimeClient { void setTime(int hour, int minute, int second); void setDate(int day, int month, int year); void setDateAndTime(int day, int month, int year, int hour, int minute, int second); LocalDateTime getLocalDateTime(); static ZoneId getZoneId (String zoneString) { try { return ZoneId.of(zoneString); } catch (DateTimeException e) { return ZoneId.systemDefault(); } } default ZonedDateTime getZonedDateTime(String zoneString) { return ZonedDateTime.of(getLocalDateTime(), getZoneId(zoneString)); } }

Default Methodspublic interface TimeClient { void setTime(int hour, int minute, int second); void setDate(int day, int month, int year); void setDateAndTime(int day, int month, int year, int hour, int minute, int second); LocalDateTime getLocalDateTime(); static ZoneId getZoneId (String zoneString) { try { return ZoneId.of(zoneString); } catch (DateTimeException e) { return ZoneId.systemDefault(); } } default ZonedDateTime getZonedDateTime(String zoneString) { return ZonedDateTime.of(getLocalDateTime(), getZoneId(zoneString)); } } https://docs.oracle.com/javase/tutorial/java/IandI/defaultmethods.html

Lambdas

JButton testButton = new JButton("Test Button"); testButton.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent e){ System.out.println("Click Detected by Anon Class"); } });

Lambdas

JButton testButton = new JButton("Test Button"); testButton.addActionListener(e -> System.out.println("Click Detected by Lambda Listner"));

http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/Lambda-QuickStart/index.html

Lambdas with Streamsroster .stream() .filter( p -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25) .map(p -> p.getEmailAddress()) .forEach(email -> System.out.println(email));

Lambdas with Stream

Q: print emails of male persons between 18-25 years old from

a source of objects…

Lambdas with Streampublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

public int getAge() {} public void printPerson() {} }

Q: print emails of male persons between 18-25 years old from

a source of objects…

Lambdas with Streamsroster .stream() .filter( p -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25) .map(p -> p.getEmailAddress()) .forEach(email -> System.out.println(email));

Lambdas with Streamsroster .stream() .filter( p -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25) .map(p -> p.getEmailAddress()) .forEach(email -> System.out.println(email));

Lambdas with Streamsroster .stream() .filter( p -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25) .map(p -> p.getEmailAddress()) .forEach(email -> System.out.println(email));

Lambdas with Streamsroster .stream() .filter( p -> p.getGender() == Person.Sex.MALE && p.getAge() >= 18 && p.getAge() <= 25) .map(p -> p.getEmailAddress()) .forEach(email -> System.out.println(email));

https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html

Method References

Lambdas are great for anon methods…

but what if the method already exists..

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

}

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

}

Array.sort(personArray, ???)

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

}

class PersonAgeComparator implements Comparator<Person> { public int compare(Person a, Person b) { return a.getBirthday().compareTo(b.getBirthday()); } }

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

}

class PersonAgeComparator implements Comparator<Person> { public int compare(Person a, Person b) { return a.getBirthday().compareTo(b.getBirthday()); } }

Arrays.sort(rosterAsArray, new PersonAgeComparator());

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

}

class PersonAgeComparator implements Comparator<Person> { public int compare(Person a, Person b) { return a.getBirthday().compareTo(b.getBirthday()); } }

Arrays.sort(rosterAsArray, (Person a, Person b) -> { return a.getBirthday().compareTo(b.getBirthday()); } );

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

public static int compareByAge(Person a, Person b) { return a.birthday.compareTo(b.birthday); } }

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

public static int compareByAge(Person a, Person b) { return a.birthday.compareTo(b.birthday); } }

Arrays.sort(rosterAsArray, compareByAge);

Method Referencespublic class Person { public enum Sex { MALE, FEMALE } String name; LocalDate birthday; Sex gender; String emailAddress;

public static int compareByAge(Person a, Person b) { return a.birthday.compareTo(b.birthday); } }

Arrays.sort(rosterAsArray, Person::compareByAge);

https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html

Repeatable Annotations

public @interface Schedule { String dayOfMonth() default "first"; String dayOfWeek() default "Mon"; int hour() default 12; }

@Schedule(dayOfMonth=“last”, dayOfWeek="Fri", hour="23") public void doPeriodicCleanup() { ... }

Repeatable Annotations@Repeatable(Schedules.class) public @interface Schedule { String dayOfMonth() default "first"; String dayOfWeek() default "Mon"; int hour() default 12; }

@Schedule(dayOfMonth=“last”) @Schedule(dayOfWeek="Fri", hour="23") public void doPeriodicCleanup() { ... }

public @interface Schedules { Schedule[] value(); }

https://docs.oracle.com/javase/tutorial/java/annotations/repeating.html

Type Annotations

Pre Java 8, annotations could only be applied to declarations

With Java 8, annotations can also be applied to any type use

@NonNull String str;

https://docs.oracle.com/javase/tutorial/java/annotations/type_annotations.html

how is this possible?!?

JSR-292

introduced with Java 7

new instruction on JVM! invokedynamic

new Java API (java.lang.invoke)

new classes (MethodType, MethodHandle…)

Invoking methods - reflectionObject str, Object from, Object to; Method m = str.getClass().getMethod(“replace”, from.getClass, to.getClass));

m.invoke(str, from, to);

Invoking methods - invokeExactObject str, Object from, Object to; Method m = str.getClass().getMethod(“replace”, from.getClass, to.getClass));

MethodHandles.Lookup lookup = MethodHandles.lookup(); MethodHandle mh = lookup.unreflect(method); mh.asType(mt.generic());

mh.invokeExact(str, from, to);

Invoking methods - invokeGenericObject str, Object from, Object to; Method m = str.getClass().getMethod(“replace”, from.getClass, to.getClass));

MethodHandles.Lookup lookup = MethodHandles.lookup(); MethodHandle mh = lookup.unreflect(method); mh.asType(mt.generic());

mh.invokeGeneric(str, from, to);

https://www.youtube.com/watch?v=STDBY5kT4_M

Invoke Dynamic

provides linking at runtime

directly translates to VM

used in lambdas*

Jack & Jill

enable Java 8 with Jack

Jack shrinks, obfuscates, repackages, multidex

Jill translates jar files to Jack

Jack

javac: java to class dx: class to dex

Jack: java to jack to dex

Jack can handle Lambdas… goodbye RetroLambda

Proguard included!

Enable Jack!android { ... defaultConfig { ... jackOptions { enabled true } } compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } }

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thanks!! @yenerm