Java 11 is the new Java release and, differently from Java 9 and Java 10, it is a "Long Term Support" release - we will see what that means exactly. This presentation details the main new features of Java 11, starting from licensing (where there are important changes - in particular the Oracle JDK may only be used in production if you have a support contract with Oracle), to arrive to the new Java 11 features, with a quick peek back at what was introduced in Java 9 and Java 10. The main Java 11 arguments are: • Two new garbage collectors: EpsilonGC e ZGC • Support for TLS 1.3 • Possibility to execute a single source file • New HTTP client based on the Flow API • Removal of modules (CORBA, JTA, @Inject, ecc.) • Bytecode news (nest-mates, dynamic constants)

1. sbordet@webtide.com
Java 9/10/11
What’s new and why you should upgrade
@simonebordet

2. sbordet@webtide.com
Simone Bordet
● @simonebordet
● sbordet@webtide.com
● Java Champion
● Works @ Webtide
○ The company behind Jetty and CometD

3. sbordet@webtide.com
Java 11
● Java 11 is here!
● “Long Term Support” (LTS) Release
○ Java 8 was the previous LTS Release
○ Java 9 and Java 10 already unmaintained

4. sbordet@webtide.com
Java 11
OpenJDK 11 Repository
https://hg.openjdk.java.net
Oracle JDK Binary
https://java.oracle.com
OpenJDK Binary
http://jdk.java.net/11
RedHat JDK
Binary
Azul JDK Binary (Zulu)
AdoptOpenJDK Binary
https://adoptopenjdk.net

5. sbordet@webtide.com
Java 11
● What does LTS really mean?
● During the 6 months of “life” of a Java 11:
○ OpenJDK Binary -> GPL
○ AdoptOpenJDK -> GPL
○ Azul Zulu -> GPL
○ Oracle JDK Binary -> Oracle License
■ MUST PAY Oracle for production use

6. sbordet@webtide.com
Java 11
● After the 6 months of “life” of a Java 11:
○ Upgrade to Java 12
○ Stay on Java 11

7. sbordet@webtide.com
● After 6 months, you stay on Java 11
○ Never update -> exposed to vulnerabilities
○ Update Java 11 -> 11.0.x
● Community (RedHat) backports fixes
● Vendors create binary builds
○ AdoptOpenJDK -> GPL
○ Other vendors (Oracle, Azul, RedHat, …) -> PAY
Java 11

8. sbordet@webtide.com
Java 9
New Features

9. sbordet@webtide.com
Java 9
● Java 9 introduced the Java Module System
● Along with it, a number of breaking changes
○ Upgrading from 8 to 9/10/11 is NOT simple
○ Many runtime behavior changes
○ Needs very thorough testing

10. sbordet@webtide.com
Java 9
● Removed tools.jar
○ Attach API, Compiler API, JavaDoc API, etc.
● Removed JavaDB
● Removed endorsed and extension directories
○ $JAVA_HOME/lib/endorsed
○ $JAVA_HOME/jre/lib/ext

11. sbordet@webtide.com
Java 9
● Class loading implementation changed
○ Different behavior to support modules
ClassLoader sysCL = ClassLoader.getSystemClassLoader();
// Throws ClassCastException now!
URLClassLoader urlCL = (URLClassLoader)sysCL;

12. sbordet@webtide.com
Java 9
● Loading resources
URL resource = sysCL.getResource("java/lang/String.class");
// Not a file:/ nor a jar:/ URL!
resource = jrt:/java.base/java/lang/String.class
URL resource = sysCL.getResource("/com/foo/bar.properties");
// It’s there, but it won’t find it!
resource = null;

13. sbordet@webtide.com
Java 9
● New version string scheme
○ 1.8.0_181 -> 9.0.1
○ Broke many Maven Plugins, Jetty, etc.
● JDK 9’s java.lang.Runtime.Version class
○ Cannot parse JDK 8 version string
○ Must implement custom parsing to support both

14. sbordet@webtide.com
Java 9
● Internal APIs encapsulated
○ Cannot access sun.* or com.sun.* classes
● Finalization
○ sun.misc.Cleaner -> java.lang.ref.Cleaner
○ Object.finalize() -> deprecated
● Unsafe
○ Some sun.misc.Unsafe usage replaced by VarHandle

15. sbordet@webtide.com
Java 9
● Multi Release jars
com/
acme/
A.class
B.class
META-INF/
versions/
9/
com/
acme/
A.class <- Replaces normal A.class
C.class

16. sbordet@webtide.com
Java 9
● Variable Handles
○ Expose some Unsafe functionality
class ConcurrentLinkedQueue_BAD {
// BAD, adds indirection
AtomicReference<Node> head;
}

17. sbordet@webtide.com
Java 9
class ConcurrentLinkedQueue {
private Node head;
private static final VarHandle HEAD;
static {
HEAD = MethodHandles.lookup()
.findVarHandle(ConcurrentLinkedQueue.class,
"head", Node.class);
}
public void m() {
if (HEAD.compareAndSet(...))
...
}
}
}

18. sbordet@webtide.com
Java 9
● Process APIs
Process p = new ProcessBuilder()
.command("java")
.directory(new File("/tmp"))
.redirectOutput(Redirect.DISCARD)
.start();
ProcessHandle.of(p.pid())
.orElseThrow(IllegalStateException::new)
.onExit()
.thenAccept(h ->
System.err.printf("%d exited%n", h.pid())
);

19. sbordet@webtide.com
Java 9
● Concurrent APIs Enhancements
○ java.util.concurrent.Flow
■ Identical APIs and semantic of ReactiveStreams
○ CompletableFuture enhancements
■ Common scheduler for timeout functionalities
CompletableFuture.supplyAsync(() -> longJob())
.completeOnTimeout("N/A", 1, TimeUnit.SECONDS)
CompletableFuture.supplyAsync(() -> longJob())
.orTimeout(1, TimeUnit.SECONDS)

20. sbordet@webtide.com
Java 9
● jshell - Read-Eval-Print-Loop (REPL)
● Pretty powerful!
○ AutoCompletion, Imports, Javadocs
○ History, search
○ Syncs with external editor
○ Function and forward references
○ ...

21. sbordet@webtide.com
Java 9
● G1 is the default Garbage Collector
● Much improved from 8 and even better in 11
○ Adaptive start of concurrent mark
○ Made internal data structures more concurrent
○ More phases parallelized
○ Reduced contention
○ Reduced memory consumption

22. sbordet@webtide.com
Java 9
● Unified GC logging
○ Not compatible with previous GC logs
● Every GC logs differently
● Example
○ -
Xlog:gc*,ergo*=trace,ref*=debug:file=log
s/gc.log:time,level,tags

23. sbordet@webtide.com
Java 9
● JVM options changes
○ 50 options removed - JVM refuses to start
○ 18 options ignored - 12 options deprecated
● Must review your command line!
○ Especially if you had custom GC tuning options

24. sbordet@webtide.com
Java 10
New Features

25. sbordet@webtide.com
Java 10
● Local variable type inference (a.k.a. var)
○ http://openjdk.java.net/projects/amber/LVTIstyle.html
// Infers ArrayList<String>
var list = new ArrayList<String>();
// infers Stream<String>
var stream = list.stream();

26. sbordet@webtide.com
Java 10
● var is not a keyword, it is a reserved type name
○ It’s a valid identifier, unless used in places where the
compiler expects a type name
int var = 13;

27. sbordet@webtide.com
Java 10
● Good var usage
var message = "warning, too many features";
var anon = new Object() {
int count = 0;
}
anon.count++; // Compiles!

28. sbordet@webtide.com
Java 10
● Controversial var usage
// What type ?
var result = processor.run();
// IDE cannot help you
var list = new <ctrl+space>

29. sbordet@webtide.com
Java 10
● Experimental Graal JIT
○ https://www.graalvm.org/
● -XX:+UnlockExperimentalVMOptions -XX:
+UseJVMCICompiler
● Not yet recommended in production
○ Twitter uses it in production, you may too (YMMV)

30. sbordet@webtide.com
Java 10
● Docker awareness
○ On by default
○ https://blog.docker.com/2018/04/improved-docker-containe
-XX:-UseContainerSupport
-XX:ActiveProcessorCount=n
-XX:MinRAMPercentage=p
-XX:InitialRAMPercentage=p
-XX:MaxRAMPercentage=p

31. sbordet@webtide.com
Java 11
New Features

32. sbordet@webtide.com
Java 11
● Two new Garbage Collectors
○ Epsilon GC
○ ZGC
● Epsilon GC
○ No-operation GC

33. sbordet@webtide.com
● ZGC
○ 5 years of closed source development @ Oracle
○ XX:+UnlockExperimentalVMOptions XX:+UseZGC
○ Single Generation, Region Based
○ Concurrent Marking
○ Concurrent Compaction
○ Very low STW pause times
Java 11

34. sbordet@webtide.com
Java 11
● Removed methods
○ Thread.stop(Throwable)
○ Thread.destroy()
○ System.runFinalizersOnExit(boolean)
○ Some SecurityManager.check*() methods

35. sbordet@webtide.com
Java 11
● Removed modules
○ java.activation (JAF)
○ java.corba
○ java.transaction (JTA)
○ java.xml.bind (JAXB)
○ java.xml.ws (JAX-WS)
○ java.xml.ws.annotation (@PostConstruct, ...)
● Replaced by standalone jars
○ https://dzone.com/articles/apis-to-be-removed-from-java-11

36. sbordet@webtide.com
Java 11
● Java Flight Recorder
○ Open Sourced by Oracle, included in OpenJDK 11
○ java -XX:StartFlightRecording ...
● Java Mission Control
○ Open Sourced by Oracle
○ Downloads at https://jdk.java.net/jmc/
○ JMC 7 scheduled for January 2019

37. sbordet@webtide.com
Java 11
● TLS 1.3
○ More secure and recent version of TLS
○ Removed vulnerable/weak ciphers
○ Added new ciphers and algorithms
● Using SSLEngine? Verify it works!

38. sbordet@webtide.com
Java 11
● Launch Single-File Source-Code programs
$ java Hello.java
● Compiled in-memory with Graal
● Teaching
● Java Scripts

39. sbordet@webtide.com
Java 11
● HTTP client
○ Supports both HTTP/1.1 and HTTP/2
○ Based on the j.u.c.Flow APIs
HttpClient c = HttpClient.newBuilder().build();
HttpRequest r = HttpRequest.newBuilder()
.uri(...).build();
CompletableFuture<String> f = c.sendAsync(r,
BodyHandlers.ofString());

40. sbordet@webtide.com
Java 11
● Nest Mates
○ Inner (nested) classes introduced in Java 1.1
○ Outer class can access inner class
■ Via compiler tricks - bridge methods
java.lang.UnsupportedOperationException
at NestExample.init(NestExample.java)
at NestExample.access$000(NestExample.java)
at NestExample$Inner.(NestExample.java)
at NestExample.main(NestExample.java)

41. sbordet@webtide.com
Java 11
● Nest Mates
○ Now specified in the JVM Specification
○ New class file attribute
○ New reflection APIs: Class.getNestMembers(), ...
○ New JVM access controls at runtime
● Do you play with bytecode?
○ Use ASM 7+

42. sbordet@webtide.com
Conclusions

43. sbordet@webtide.com
Conclusions
● Upgrade from Java 8 takes time
○ Lots of runtime changes
● Java 8 will be soon unmaintained / unavailable
○ Skip Java 9 and Java 10 - go straight to Java 11
● Lots of good stuff and more coming
○ And coming every 6 months now!

44. sbordet@webtide.com
Questions?