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Java 11 adds a standard HTTP Client, experimental ZGC and Epsilon collectors, TLS 1.3 support, and library and runtime changes. For teams upgrading from Java 8, the biggest practical risks may be compatibility and packaging: Java 11 no longer includes Java Web Start, JavaFX, or several Java EE and CORBA modules. It does not guarantee faster applications; performance depends on the workload, collector, JDK build, and runtime settings.
What are the main new features in Java 11?
Java 11 is a long-term-support release of the Java platform, but the changes developers encounter are not all the same kind. Some are standard Java SE APIs; others belong to the HotSpot JVM or the JDK distribution. Keeping those categories separate helps avoid assuming that every runtime change is a language feature or that every feature is available in the same way across vendors.
The HTTP Client is a standard API
The HTTP Client API, incubating since JDK 9 and updated in JDK 10, became a standard Java SE API in JDK 11. Its package is java.net.http. Applications using the earlier incubator package, jdk.incubator.http, need to update imports and check any related code before moving to the standard API. Its inclusion means developers have a modern HTTP client in the JDK; it does not establish that requests will run faster than with another client.
Library and Unicode updates
Java 11 adds Collection.toArray(IntFunction), which lets a caller supply a function that creates an array of the desired runtime type. Review calls such as collection.toArray(null): overload resolution can make a call that was previously accepted ambiguous at compile time.
The JDK 11 release notes also record support for Unicode 10.0.0: 16,018 new characters, 18 new blocks, and 10 new scripts. These are figures stated in the release notes, not counts of Java language constructs.
What changed in Java 11 performance and garbage collection?
Java 11 introduced ZGC and Epsilon as experimental collectors. G1 was already the default collector from JDK 9 onward, so a move from Java 8 may change the default even though Java 11 did not introduce G1 as the default. Collector selection should be based on representative application tests, not a general claim that a newer JDK is faster.
| Collector | Java 11 role | Practical interpretation |
|---|---|---|
| G1 | Default collector in JDK 9 and later. Oracle’s migration guide describes it as low-pause oriented and says it should provide a better overall experience for most users than the JDK 8 Parallel GC default. | Java 8 users may see a collector change if they relied on defaults. Oracle’s characterization is not a performance guarantee for every application. |
| ZGC | Experimental, scalable, low-latency collector in JDK 11. The release notes state design goals of pauses no longer than 10 ms, pauses that do not increase with heap or live-set size, and support for heaps ranging from a few hundred megabytes to multiple terabytes. | These are goals in the JDK 11 implementation context, not measured results or service-level guarantees. The initial experimental release had platform and feature limitations; check documentation for the exact vendor and build. |
| Epsilon | Experimental no-op collector: it allocates memory but does not reclaim it. | Useful for selected performance tests, comparing collector costs, checking memory-pressure behavior, and some very short-lived jobs. It is not a general-purpose option for applications that need memory reclaimed. |
How to compare collectors for an application
Test the same application under representative conditions before changing a production collector. Record:
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- Pause-time distribution, including tail latency, rather than only an average.
- Throughput under the same representative load.
- Heap size and live-set size.
- CPU and memory overhead.
- Vendor, JDK build, operating system, hardware, and any platform or operational constraints.
The JDK 11 release notes describe goals and implementation changes, not an independent head-to-head benchmark. A useful performance claim therefore needs a named workload and test setup; collector design targets alone cannot predict an application’s result.
Compiler-thread management
JDK 11 dynamically manages compiler threads: the described implementation starts one compiler thread of each type at startup, then starts or stops additional threads dynamically. -XX:+UseDynamicNumberOfCompilerThreads is enabled by default in that implementation. This is a runtime thread-management change, not evidence of a general benchmark improvement.
What changes matter most when migrating from Java 8?
Migration is not just a source recompilation. Deployment technology, APIs formerly bundled with the JDK, default runtime behavior, TLS, and logging can all affect a Java 8 application. Oracle’s Java 11 migration guidance recommends first running the existing program, then updating third-party libraries, compiling if needed, and using jdeps as part of preparation.
- Run the existing application on the target JDK. Exercise its normal workflows and capture startup, class-loading, TLS, and logging failures before changing code.
- Inventory removed deployment and runtime components. Search build files, scripts, packaging, and operations documentation for the items listed below.
- Update third-party libraries. Replace dependencies that expect removed JDK modules or are incompatible with the target runtime.
- Compile and resolve source issues. Update incubator HTTP Client imports and address any overload ambiguity, including affected
toArray(null)calls. - Use
jdepsas part of dependency analysis. Review its findings alongside the actual runtime tests; static dependency analysis does not replace exercising the application. - Test on the exact vendor and update build intended for deployment. Record the build and operating environment with results, particularly for TLS and collector behavior.
Removed deployment technologies
Java 11 removed applet and Java Plug-in support, Java Web Start, and the javaws launcher. Find any applet deployment, browser plug-in, Web Start launch, or operational script that depends on these technologies. Such applications need a different deployment approach; installing Java 11 alone will not restore the removed components.
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Java EE and CORBA modules are no longer bundled
Code that depended on APIs supplied by Java EE or CORBA modules in earlier JDKs may fail to compile or may fail at runtime with missing classes or modules. The migration guide identifies, among others:
- JAXB:
java.xml.bind. - JAX-WS and SAAJ:
java.xml.ws. - Web-services annotations.
- CORBA and the related transaction subset.
Identify which of these APIs the application actually uses, then add and manage the required dependencies separately or change the affected integration. Oracle’s migration guide notes that JAXB and JAX-WS can be downloaded from Maven; the application still needs compatible dependencies and deployment configuration.
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JavaFX is separate
JavaFX is no longer bundled with the JDK. If a build, installer, or runtime assumes it is included, treat JavaFX as a separate dependency and plan how it will be obtained and packaged for the target environment.
Garbage-collection flags and logs
JDK 11 uses unified JVM logging for garbage-collection logs. Existing flags, scripts, dashboards, and log parsers may need changes. The migration guide gives -Xlog:gc as the unified logging form and marks -XX:+PrintGCDetails and -XX:+PrintGC deprecated. Review old CMS-related flag combinations and removed options as well rather than carrying Java 8 startup arguments forward unchanged.
TLS and certificate behavior
TLS 1.3 is implemented and enabled by default in JDK 11. Test connections against the services the application actually uses, and review truststores, disabled algorithms, and certificate chains. Successful behavior on one JDK update does not prove that a later update has identical trust decisions.
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For example, Oracle’s JDK 11.0.31 update notes, released April 21, 2026, specify rejection of TLS server certificates anchored by listed Chunghwa roots when those certificates were issued after March 17, 2026. This is a dated update-level trust-store change, not a feature introduced in the original Java 11 release. Check the release notes for the precise vendor and update being deployed.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is Java 11 faster than Java 8?
There is no universal yes-or-no answer established by the platform changes alone. A migration can change the default collector from Java 8’s Parallel GC to G1, and Java 11 includes runtime changes such as dynamic compiler-thread management. ZGC also has stated low-pause design goals. None of those facts is a benchmark of a particular service, and they do not establish that its throughput, latency, or resource use will improve.
For a meaningful comparison, keep the workload and environment controlled and report the JDK vendor and exact update, hardware and operating system, application version, request or job mix, heap and live-set conditions, collector settings, warm-up, throughput, pause-time distribution, and CPU and memory use. If the results differ, describe the measured conditions rather than generalizing them to all Java applications.
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The standard HTTP Client and the collection API addition are Java SE API changes. Unicode support is a platform data update. ZGC and Epsilon were experimental HotSpot collectors in JDK 11, while G1’s default status and dynamic compiler-thread behavior concern runtime implementation. Removed deployment tools and formerly bundled modules affect the JDK distribution and packaging. TLS defaults and trust behavior depend on the JDK release and update as well as the application’s configuration.
That distinction matters when moving between vendors or later Java 11 updates: do not assume that an experimental collector, implementation flag, bundled component, or certificate decision has identical availability and behavior everywhere. Verify it against the precise runtime build used in production.
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