Java 9/10/11 - What's new and why you should upgrade
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The document outlines the new features and key changes in Java 9, 10, and 11, emphasizing the transition from Java 8 and the importance of upgrading to Java 11, which is a long-term support release. It discusses improvements like the Java module system, local variable type inference, enhancements in garbage collection, and the inclusion of new APIs and features. The author advises that while upgrading may be complex due to runtime changes, sticking to Java 8 is not advisable as it will soon be unsupported.
Java 9/10/11 - What's new and why you should upgrade
- 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
- 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
- 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
- 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+
- 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!