java8

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Summary

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• New features and concepts

• New and extended APIs

• Performance improvements

• Conclusion

• Q & A

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New features and concepts

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• Interface changes

• Lambda expressions

• Streams

• Nashorn

• Java FX improvements

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Interface changes

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• Interfaces can now define static methods:

• Interfaces can now define default methods:

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Interface changes

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• Functional interfaces:• An interface is functional if it defines exactly one abstract

method.

• Default and static methods are not abstract, so they can be

defined without compile errors.

• This annotation has been introduced to declare interfaces as

functional: @FunctionalInterface

• Runnable, Comparator or Cloneable are some examples of

functional interfaces.

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Lambda expressions

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• Functional Interfaces + Lambda Probably the biggest feature

since generics.

• They are basically used to instantiate functional interfaces, for

instance:

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Lambda expressions

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• Concrete examples:

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Lambda expressions

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• A lambda is compatible with a functional interface when their

inputs, output and checked exceptions match.

• Lambdas can capture variables outside the lambda body if the

variables are effectively final.

• Lambdas can’t be used to control the flow of the application:

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Lambda expressions

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• Advantadges:

• Less code to write.

• Flexibility to instantiate interfaces.

• Alternative to anonymous inner classes.

• Disadvantages:

• More difficult to debug.

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Streams

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• A sequence of elements supporting sequential and parallel

aggregate operations.

• A stream can be used just once.

• The most common way to obtain a stream is from collections:

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Streams

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• Two kind of operations:

• Intermadiate: Keep the stream open and allow to concatenate

operations with the same stream.

• Some of them: Filter, map, flatMap, peek, distinct, sorted,

etc.

• Terminal: It must be the final operation, once this one is

executed, the stream is consumed and is no longer available.

• Some of them: forEach, toArray, reduce, collect, sum, min,

max, etc.

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Streams

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• A couple of examples:

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Nashorn

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• New JS engine, Rhino’s successor.

• Ability to access Java classes from JS… and

viceversa.

• Nashorn + Avatar.js Node.js functionality

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Nashorn

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• Why use Nashorn (extracted from Oracle):• Can reuse existing Java libraries and middleware

• Can take advantage of multiple cores

• Can be secured using the Java security model

• Can be managed using existing Java tools

• VisualVM, MBeans, Flight Recorder, Mission Control

• Can access Java Platform APIs to complement node APIs

• BigInteger, Date, Calendar, XML, SQL, Multicast, etc

• Small enough for embedded usage (less than 2Mb)

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JavaFX improvements

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• It is the sustitute of Swing and it has been

improved in java 8.

• New look with Modena theme.

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JavaFX improvements

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• True 3D support.

• Video & audio recording.

• Printing support

• Added new controls

• Fully open source.

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New and extended APIs

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• New java.time API

• java.util.function

• Collection API additions

• Other additions

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New java.time API

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• Similar to JodaTime library.

• Instead of include JodaTime in the JDK, it was

redesigned from scratch.

• Useful value types:• LocalDateTime, LocalDate, LocalTime.

• Year, Month, YearMonth. MonthDay, DayOfWeek.

• Instant, Period, ZonedDateTime.

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Java.util.function

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• Set of functional interfaces widely used in the new APIs of Java 8.

• Here are a few:

• Function<T, R> - take a T as input, return an R as ouput.

• Predicate<T> - take a T as input, return a boolean as output.

• Consumer<T> - take a T as input, perform some action and

don't return anything.

• Supplier<T> - with nothing as input, return a T.

• BinaryOperator<T> - take two T's as input, return one T as

output, useful for "reduce" operations.

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Colletion API additions

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• The ability that interfaces can define default methods have

introduced a lot of additionson the colletion interfaces. Some of

them:

• Iterable.forEach(Consumer)

• Iterator.forEachRemaining(Consumer)

• Collection.removeIf(Predicate)

• Collection.spliterator()

• List.sort(Comparator)

• List.replaceAll(UnaryOperator)

• Map.forEach(BiConsumer)

• …

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Other additions

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• There are several additions with a lot of new classes and new

methods:

• Concurrency API additions.

• IO/NIO API additions.

• New methods and classes in java.lang, java.util and in several places more.

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Conclusion

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• A lot of additions in this release.

• Lambdas and functional interfaces will change a little bit the way

people is developing.

• But several of them were already in antoher languages, so Oracle

has not invented nothing new.

• It seems that they have worked really hard to improve

performance, let’s see if it is true!!!

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References

• http://docs.oracle.com/javase/8/docs/api/overview-summary.html

• http://www.techempower.com/blog/2013/03/26/everything-about-

java-8/

• http://www.infoq.com/articles/nashorn

• https://avatar.java.net/

• http://java.dzone.com/articles/whats-new-java-8-part-i-javafx

• https://blogs.oracle.com/thejavatutorials/entry/

learn_more_about_performance_and

java8

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