"Highlights from Java 10&11 and Future of Java" at Java User Group Bonn 2018 by Vadym Kazulkin

Highlights from Java 10 and 11
and Future of Java
by Vadym Kazulkin, ip.labs GmbH

Contact
Vadym Kazulkin, ip.labs GmbH
v.kazulkin@gmail.com
www.xing.com/profile/Vadym_Kazulkin
@VKazulkin

JEP 286 (Project Amber)
Local-Variable Type Inference
var list = new ArrayList<String>(); // infers ArrayList<String>
var stream = list.stream(); // infers Stream<String>
strictly speaking
var list = new ArrayList<String>()
is the same as
ArrayList<String> list = new ArrayList<String>();
List<String> list = new ArrayList<String>();
is the same as
var list = (List<String>) new ArrayList<String>()

JEP 307
Parallel Full GC for G1
Goal:
● Improve G1 worst-case latencies (when the concurrent collections can't
reclaim memory fast enough) by making the full GC parallel.

JEP 304
Garbage Collector Interface
Goals:
● Better modularity for HotSpot internal GC code
● Make it simpler to add a new GC to HotSpot without perturbing the current
code base
● Make it easier to exclude a GC from a JDK build

JEP 317
Experimental Java-Based JIT Compiler
Graal, a Java-based JIT compiler on the Linux/x64 platform, is the basis of the
experimental Ahead-of-Time (AOT) compiler introduced in JDK 9.
To Enable:
-XX:+UnlockExperimentalVMOptions -XX:+UseJVMCICompiler

Miscellanious API Changes
Better container-awareness
● Before later versions of Java 8
– Runtime.getRuntime().availableProcessors() -> retrieves value from sysconf, means the total
number of processors for VM
– Runtime.getRuntime().maxMemory() -> gets the value for VM overall memory
● Java 9 is container-aware automatically detecting cpusets
JVM considers cgroups memory limits if the following flags are specified:
– -XX:+UseCGroupMemoryLimitForHeap
– -XX:+UnlockExperimentalVMOptions
– Max Heap space will be automatically set (if not overwritten) to the limit specified by the cgroup

Better container-awareness
● For “fixing” CPU shares in Java 9 overwrite
– -XMX for memory
– -XX:ParallelGCThreads and -XX:ConcGCThreads for CPU
– -System property java.util.concurrent.ForkJoinPool.common.parallelism for ForkJoinPool
● Better container-awareness in Java 10 (CPU shares support is included)
– Runtime.getRuntime().availableProcessors()
– Runtime.getRuntime().maxMemory()
Sources: „Java SE 9 support for Docker CPU and memory limits“https://blogs.oracle.com/java-platform-group/java-se-support-for-
docker-cpu-and-memory-limits
„ Nobody puts Java in a container” https://jaxenter.com/nobody-puts-java-container-139373.html
„Improve docker container detection and resource configuration usage” https://bugs.openjdk.java.net/browse/JDK-8146115
„ Better containerized JVMs in JDK 10” https://jaxenter.com/better-containerized-jvms-jdk-10-140593.html

● java.util.List, Set, Map.copyOf(Collection)
● java.util.stream.Collectors.toUnmodifiableList/Set/Map(Stream)
● Optional.orElseThrow()

Long-Term Support
Sources: https://jaxenter.de/jdk-support-sag-mal-70294 & Azul Systems
https://www.oracle.com/corporate/pressrelease/java-se-subscription-offering-062118.html
https://www.infoq.com/news/2018/06/new-support-pricing-java

Extended Oracle Public Java SE 8 Support
Source: http://www.oracle.com/technetwork/java/javase/tech/eol-135779.html

AdoptOpenJDK
Source: https://adoptopenjdk.net/

JEP 323 (Project Amber)
Local-Variable Syntax for Lambda Parameters
● (x, y) -> x.process(y) // implicitly typed lambda expression
● (var x, var y) -> x.process(y) // implicit typed lambda expression
● (@NonNull var x, @NonNull var y) -> x.process(y)

JEP 318
Epsilon: A No-Op Garbage Collector
Goals:
● Provide a completely passive GC implementation with a bounded
allocation limit and the lowest latency overhead possible, at the expense of
memory footprint and memory throughput
● Measure performance of other GCs

JEP 321
HTTP Client
Goals:
● Standardize the incubated HTTP Client API introduced in JDK 9, via JEP
110, and updated in JDK 10
● HTTP 2.0 Support

JEP 332
Transport Layer Security 1.3
Goal:
● Implement version 1.3 of the Transport Layer Security (TLS) Protocol

● File.isSameContents() in addition to File.isSameFile()
● New methods and behaviour on the Java String class
– trim() method : uses the definition of space as any codepoint that is less than or equal to the
space character codepoint (u0040.)
– String.lines() and String.strip() also use this definition
– isBlank() : true if the string is empty or contains only white space
– stripLeading(), stripTrailing() : removal of Unicode white space from the beginning/end
Sources: https://bugs.openjdk.java.net/browse/JDK-8202285
https://www.javacodegeeks.com/2018/05/new-jdk-11-files-method-issamecontent.html

Project Amber
Simplifying syntax (continuing)
Source: http://openjdk.java.net/projects/amber/

JEP 305
Pattern Matching
int numberOfLetters;
switch(season) {
case FALL:
numberOfLetters=4;
break;
case WINTER:
case SPRING:
case SUMMER:
numberOfLetters=6;
break;
default:
throw new IllegalStateException(„unknown season “+season);
}

JEP 305
Pattern Matching
int numberOfLetters =switch(season) {
case FALL -> 4;
case WINTER, SPRING, SUMMER -> 6;
default -> throw new IllegalStateException(„unknown season “+season);
};

JEP 305
Pattern Matching
String formatted = "unknown";
if (obj instanceof Integer) {
int i = (Integer) obj;
formatted = String.format("int %d", i);
} else if (obj instanceof Byte) {
byte b = (Byte) obj;
formatted = String.format("byte %d", b);
} else if (obj instanceof Long) {
long l = (Long) obj;
formatted = String.format("long %d", l);
} else if (obj instanceof Double) {
double d = (Double) obj;
formatted = String.format(“double %f", d);
} else if (obj instanceof String) {
String s = (String) obj;
formatted = String.format("String %s", s); }

JEP 305
Pattern Matching
String formatted;
switch (obj) {
case Integer i: formatted = String.format("int %d", i);
break;
case Byte b: formatted = String.format("byte %d", b);
break;
case Long l: formatted = String.format("long %d", l);
break;
case Double d: formatted = String.format(“double %f", d);
break;
case String s: formatted = String.format("String %s", s);
break;
default: formatted = obj.toString();
}

Project Valhalla
Value types and specialised generics
Source: http://openjdk.java.net/projects/valhalla/

Project Valhalla
Value Object
Value Object is an immutable type that is distinguishable only
by the state of its properties

Project Valhalla
Source: https://dzone.com/articles/what-is-project-valhalla

Project Valhalla
Benefits:
● Reduced memory usage
● Reduced indirection
● Increased locality
Codes like a class, works like a primitive (Brian Goetz)

Project Valhalla
Value Types
value class Point {long x, y ;}

Project Valhalla
Value Types
Can
● have method and field
● implement interfaces
● use encapsulation
● be generic
Can’t
● be muted
● be sub-classed

Project Valhalla
Specialized Generics
List<Long> points= new ArrayList<Long>();
List<Point> points= new ArrayList<Point>();
class Box<any T> { T value; }
class Box{T=Long} { Long value; }
class Box{T=Point} { Point value; }
Source: John Rose: http://cr.openjdk.java.net/~jrose/values/value-type-hygiene.html

Project Metropolis
Polyglot GraalVM (current version 1.0-rc3)
Source: http://openjdk.java.net/projects/metropolis

Project Metropolis
Goals:
● High performance for all languages
● Zero overhead interoperability between languages
● Language-level virtualization level for shared tooling
Source: Oleg Selajev : “Run Code in Any Language Anywhere with GraalVM” https://www.youtube.com/watch?v=JoDOo4FyYMU

GraalVM
Architecture
Sources: Practical Partial Evaluation for High-Performance Dynamic Language Runtimes
http://chrisseaton.com/rubytruffle/pldi17-truffle/pldi17-truffle.pdf
„The LLVM Compiler Infrastructure“ https://llvm.org/

Project Sulong
Source: Thomas Würthinger : “One VM to Rule Them All” https://www.youtube.com/watch?v=mMmOntDWSgw

GraalVM
Polyglot Server Example
Source: https://www.graalvm.org/docs/examples/polyglot-javascript-java-r/
JavaScript
Java
R
JavaScript

GraalVM
Performance

SubstrateVM
Source: Christian Wimmer : “Polyglot Native: Java, Scala, Kotlin, and JVM languages” https://www.youtube.com/watch?v=5BMHIeMXTqA

SubstrateVM

Difference Between Substrate VM & JVM Models
Source: Kevin Menard : “Improving TruffleRuby’s Startup Time with the SubstrateVM” https://www.youtube.com/watch?v=hIMldcAzd5o

GraalVM on SubstrateVM
A game changer for Java & Serverless?
Cold Start :
Source: Ajay Nair „Become a Serverless Black Belt” https://www.youtube.com/watch?v=oQFORsso2go

AWS Lambda cold start time
by supported language
Source: Yan Cui: https://read.acloud.guru/does-coding-language-memory-or-package-size-affect-cold-starts-of-aws-lambda-a15e26d12c76

GraalVM on SubstrateVM
A game changer for Java & Serverless?
Java Function compiled into a native executable using GraalVM on
SubstrateVM reduces
● “cold start” times
● memory footprint
by order of magnitude compared to running on JVM.

Project Loom
Fibers and Continuations
Source: http://openjdk.java.net/projects/loom

Project Loom
Goals:
● explore and incubate Java VM features and APIs built on top of them for
the implementation of lightweight user-mode threads (fibers), delimited
continuations

Project Loom
Fibers
Fibre is a thread scheduled not by the OS, but by the Runtime

Project Loom
Fibers
2 options how to implement:
● Thread (Runnable, ThreadSchedular)
● Strand (abstract thread)
Fiber Thread
Source: Talk „Project Loom: Fibers and Continuations for the Java Virtual Machine“ by Ron Pressler
https://www.youtube.com/watch?v=fpyub8fbrVE

Project Loom
Continuation
Continuation is a program object, representing a computation
that may be suspended and resumed

Project Loom
Continuations
foo() { // (2)
...
bar()
...
}
bar() {
...
Continuation.yield() // suspend (3)
... // (5)
}
main() {
Continutation c = new Continuation(foo) // (0)
c.continue() // (1)
c.continue() // (4)
}
Sources: Proposal by Ron Pressler: http://cr.openjdk.java.net/~rpressler/loom/Loom-Proposal.html and
Parallel Universe Quasar Project http://docs.paralleluniverse.co/quasar/

Project Loom
Continuations
Thread
=
Continuation + Schedular

Project Loom
Fibers Use Cases
● Fibers are serializable
– fibers can be sent via network
– advantages when calling external APIs in serverless environment
– shutdown container after sending request, startup after the response arrived and save money
(pause-resume functionality is currently missing for serverless)
● Retriable exceptions

Projects Panama
Goal:
● improve and enrich the connections between the JVM and well-defined non-Java
APIs, including many interfaces commonly used by C programmers
Sources: http://openjdk.java.net/projects/panama
Talk by Jim Laskey: “Native Script Engine or Go Panama” https://www.youtube.com/watch?v=-JLhwsbMvjQ

Project Shenandoah
Goals :
● ultra-low pause time garbage collector that reduces GC pause times by
performing more garbage collection work concurrently with the running Java
program
● CMS and G1 both perform concurrent marking of live objects. Shenandoah adds
concurrent compaction
Sources: http://openjdk.java.net/projects/shenandoah
Talk by Alexey Shipilev: “Shenandoah: The Garbage Collector That Could” https://www.youtube.com/watch?v=VCeHkcwfF9Q

is still an interesting and great
programming language

"Highlights from Java 10&11 and Future of Java" at Java User Group Bonn 2018 by Vadym Kazulkin

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"Highlights from Java 10&11 and Future of Java" at Java User Group Bonn 2018 by Vadym Kazulkin