Post on 08-Sep-2014
description
About author• Works in IT since 2000• 11 year of Java SE/EE experience• Occupied senior Java developer/Team Lead
positions• Winner of 2013 JBoss Community Recognition
Award. https://www.jboss.org/jbcra
About author• 6 times speaker at Odessa Java User Group• 2 times speaker at JEEConf (2013 and 2014) in
Kiev• Speaker at Java Breeze 2013 in Odessa• Speaker at Java Day 2014 in Minsk• Works 2 years as Java lector
Java 8• Java 8 has been influenced by Scala much more
than how Scala has been influenced by Java• Most expected Java release ever
JVM-based languages
Functional languages
Java 8• Code name Kenai• Specification JSR-337• Inspired by Scala, Google Guava and Joda Time
Java 8• Project Lambda• Streams API• Functional interfaces• Java time• Method references• Repeatable & time annotations• Nashorn• Accumulators
Java 8• Method Thread.stop() was deprecated in 1998
and rewritten to throw exception in 2014.
Schedule• 2012/04/26 M1 • 2012/06/14 M2 • 2012/08/02 M3 • 2012/09/13 M4 • 2012/11/29 M5 • 2013/01/31 M6 • 2013/06/13 Feature Complete• 2013/09/05 Developer Preview• 2014/01/23 Final Release Candidate• 2014/03/18 General Availability
Java 7
Java 7
Project Lambda
Project Lambda
Project Lambda
Java 7
Project Lambda
Project Lambda
Java 7
Project Lambda
Project Lambda
Project Lambda• Lambdas are not serializable• Applied to functional interfaces(with SAM)• Cannot use this• Not applied to abstract classes(even with SAM)
Project Lambda• Function• Predicate• Consumer• Supplier• BinaryOperator
Project Lambda
Interface DescriptionFunction Function with single
argument and resultPredicate Tests condition of
single argumentConsumer Performs operation
over single argumentSupplier Supplies results BinaryOperator Functions with two
arguments and results
Lambda vs Anonymous
Lambda vs Anonymous
Lambda vs Anonymous
Lambda vs Anonymous
Type Lambdas(ms)
Anonymous classes (ms)
Execution
364 329
Capturing
316 309
Linkage 354 313
Disadvantage
Java 7
Method reference
Method reference
Java 7
Streams
Streams
Streams
Streams
Java 7
Streams
Streams• Sequential• Parallel
Streams
Performance
PerformanceOperation Sequential,
secParallel,sec
Slow operation 1.0 0.4Quick operation 0.3 2.4
Parallelism level
Parallelism level• Parallel streams use ForkJoinPool to split and
combine tasks• By default number of threads is equal to number
of processors• This behavior may be overridden by changing
system property java.util.concurrent.ForkJoinPool.common.parallelism
Streams
Streams
Streams
Streams
Java 7
Streams
Stream performance
Stream performance
Iteration test
Use case Time(ms)For-each loop 35forEach(lambda) 79forEach(consumer) 12
Java 7
Default methods
Default methods
Default methods
Default methods• equals• hashCode• toString
Java 7
Java 7
Java 7
Optional
Optional
Optional
Construct date
Java 7
Java Time
Java Time
Java Time
Java Time
Java 7
Java Time
Time difference
Java Time
I/O
I/O
Encoding
Annotations
Annotations
Repeatable annotations
Repeatable annotations
Repeatable annotations
Annotations• Up to Java 7, an annotation was applied to a
declaration. • A declaration is a part of code that introduces a
new name.
Annotations• Type• Method• Field• Annotation• Package• Local variable
Type annotations
Type annotations• In Java 8, you can annotate any type use. • This can be useful in combination with tools that
check for common programming errors
Type annotations
Type annotations• Generic type arguments• Superclass and implemented interface• Constructor invocations• Casting and instanceof• Exception specifications• Wild card and type bounds
Type annotations
Nashorn
Nashorn• Based on Da Vinci Machine• Intends to enable Java developers embedding of
JavaScript in Java applications• Successor of JavaScript Rhino engine which was
started in 1997 by Netscape and maintained by Mozilla.
Java 7
Nashorn
Performance
Operation Rhino(Java 7) ,sec Nashorn (Java 8)print 3.1 0.9String operations 1.0 0.4Math operations 1.4 0.1
Collections• Improved HashMap• Balanced tree to avoid high collisions
Collections
Collections
Performance
Number of items Java 7,ms Java 81000 7 95000 67 4715000 653 40630000 2645 125250000 7842 3820
Accumulators• Scalable updatable variables. Maintaining a single
count, sum, etc., that is updated by possibly many threads is a common scalability problem.
• Added features that make ConcurrentHashMap and classes built from them more useful as caches. Better support for maps with large numbers of elements.
• Added functionality and improved performance for ForkJoinPool
Benchmark
Benchmark
Benchmark
Benchmark
Number of threads
AtomicLong LongAdder
1 236 1772 586 1384 590 468 501 4916 438 4832 459 52
Metaspace• Replacement of Permanent Generation• New JVM arguments• Resides in the heap and can be resized