Java 7 & 8

Java 7 & 8
Yannick De Turck
Ken Coenen
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Java 7 & 8
 18h15 – Java 7 (Ken)
 18h45 – Q&A
 19h – Java 8 (Yannick)
 19h30 – Q&A
 19h45 – Exercises
 20h30 – Solutions
 21h - Finish

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Java 7 (July 28th 2011)
 String in switch-statement
 Automatic resource management
 Diamond syntax
 Better Exception handling with multi-catch
 Literal enhancements
 New IO API
 Fork Join Framework
 JVM enhancements

Java 7: String in switch-statement
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Java 7: Automatic resource management
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 Try-with-resources statement
- Resources are automatically closed
 New AutoCloseable interface available to implement for your own
classes

Java 7: Automatic resource management
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Java 7: Diamond syntax
 Type Inference for Generic Instance Creation
 No longer required to repeat the type when instantiation

Java 7: Better Exception handling with multi-catch
 No longer one Exception per catch limit
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Java 7: Better Exception handling with multi-catch
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 Precise rethrowing

Java 7: Literal enhancements
 Prefix binary literals with 0b or 0B
 Use underscores in your number literals to increase readability
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Java 7: New IO API
 A whole new package: java.nio
 Non-blocking IO
 Buffer oriented instead of Stream oriented
 New classes to improve working with files
- Files
- Path
- FileSystem
- WatchService
- FileVisitor
- ...

Java 7: Fork Join Framework
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 Parallel programming
- Divide a process into smaller tasks via recursion which are handled by a
processor
- Combine the processed pieces into one result
- Divide & conquer

Java 7: Fork Join Framework
 Extend RecursiveAction or RecursiveTasks
if (my portion of the work is small enough) {
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do the work directly
} else {
split my work into two pieces
invoke the two pieces and wait for the results
}
 Practical example: ForkBlur.java

Java 7: JVM enhancements
 Support for dynamically typed languages
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- Introduction of invokedynamic
 A new bytecode instruction on the JVM for method invocation
 http://niklasschlimm.blogspot.be/2012/02/java-7-complete-invokedynamic-example.
html
- Performance improvements for other languages living in the JVM such as
Ruby, Groovy, …
 Garbage-First Collector (or G1 collector)
- Will eventually replace the Concurrent Mark-Sweep Collector (CMS)
- Advantages: works with regions, more predictable

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Java 8 (March 18th 2014)
 Lambda Expressions
 Extension Methods
 Functional Interfaces
 Method and Constructor References
 Streams and Bulk Data Operations for Collections
 Removal of PermGen
 New Date & Time API
 New Default API for Base 64 Encoding
 Improvements for Annotations
 General Performance Improvements

Java 8: Lambda Expressions
 Allows writing code in a functional style
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 Passing behaviour to a method
 Prior to Java 8: Anonymous Inner Class
 Java 8: Lambda Expressions
 Gets rid of boiler plate code
 More readable and clear code
 Type of param may be specified but isn’t obligated
(params) -> expression
() -> System.out.println(“Hello world!”);
myButton.addActionListener
() -> {
doThis();
doThat();
}((e) -> println(“Clicked!));

Java 8: Lambda Expressions
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Java 8: Extension Methods
 Add non-abstract method implementations to interfaces using the ‘default’
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keyword
 But what happens if default methods collide when using multiple interfaces?

Java 8: Extension Methods
 Override method and pick the right implementation
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Java 8: Functional Interfaces
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 @FunctionalInterface
 An interface with exactly one abstract method
 Lambda expression is applicable as implementation
 Build-in Functional Interfaces (java.util.function)
- Predicate<T>: boolean test(T t);
- Function<T>: R apply(T t);
- Supplier<T>: T get();
- Consumer<T>: void accept(T t);
- Comparator<T>: int compare(T o1, T o2);

Java 8: Functional Interfaces
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Java 8: Method and Constructor References
 Pass references of methods or constructors using the :: keyword
 Useful in combination with the Predicate class
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 Bit shorter compared to lambdas
ContainingClass::staticMethodName
ContainingObject::instanceMethodName
ContainingType::methodName
ClassName::new
String::valueOf
s::toString
String::toString
String::new

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Java 8: Streams and Bulk Data Operations for
Collections
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 java.util.Stream
 A sequence of elements on which one or more operations can be
performed
 Intermediate vs terminal operation
- Intermediate: returns the stream itself in order to be able to chain
operations
- Terminal: returns a result of a certain type
 Streams are created on a source such as a java.util.Collection
 Can be executed sequential or parallel
 Parallel utilises Fork-Join
- Watch out with long-running tasks! Blocks threads in the pool

Collections
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Collections
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 Maps
- Don’t support streams :-(
- … But they now support various new and useful methods for executing
common tasks!
 V putIfAbsent(K key, V value)
 void forEach(BiConsumer<? super K,? super V> action)
 V computeIfPresent(K key, BiFunction<? super K,? super V,?
extends V> remappingFunction)
 V computeIfAbsent(K key, Function<? super K,? extends
V> mappingFunction)
 V getOrDefault(Object key, V defaultValue)
 ...

Collections
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Collections
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 Optional<T>
- May or may not contain a non-null value
- Avoid working with null (no NPEs!)

Java 8: Removal of PermGen
 PermGen memory space completely removed
- PermSize and MaxPermSize JVM arguments are ignored and a warning
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gets displayed
 Gets replaced by Metaspace
- XX:MaxMetaspaceSize flag, default is unlimited
- System memory is the limit instead of the fixed size at startup of PermGen
- Metaspace will dynamically resize depending on demand at runtime
 Note that this does not magically fixes your memory leaks!

Java 8: New Date & Time API
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 Inspired by Joda Time
- Human time vs computer time (aka millis since epoch)
 Offers a solution to the sometimes cumbersome way of calculating
dates and time
 Interesting new classes:
- Clock
- ZoneId
- LocalDate (date without timezone)
- LocalTime (time without timezone)
- LocalDateTime (datetime without timezone)
- DateTimeFormatter
- …

Java 8: New Date & Time API
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Java 8: New Default API for Base64 Encoding
 More extensive API than the 1.6+ Base64 API
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(sun.misc.BASE64Encoder)
 3 encoders and decoders
- Basic (For regular encoding)
- URL (Encoded String needs to be used in file or url)
- MIME (MIME friendly encoding)

Java 8: New Default API for Base64 Encoding
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Java 8: Improvements for Annotations
 Annotations in Java 8 are repeatable
 @Repeatable
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Java 8: Improvements for Annotations
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Java 8: General Performance Improvements
 Performs a bit faster compared to Java 7
 Great performance improvement when making use of parallelism
 Example with Arrays.sort
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Sources
 https://github.com/yannickdeturck/workshop-java-7-8
(or shorter url: http://tinyurl.com/lzy56ng)
 Java 8 Cheatsheet: http://www.java8.org

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