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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteVirtual threads are stable in Java 25, but they have been stable since JDK 21. They can help applications handle more concurrent, waiting work—especially I/O-heavy server tasks—but they do not make individual tasks run faster or automatically improve CPU-bound code. Java 25 adds other workload-specific changes, including finalized Scoped Values, smaller object headers, AOT startup and warmup features, and new Java Flight Recorder capabilities.
Are virtual threads stable in Java 25?
Yes. Virtual threads became a permanent Java feature in JDK 21 under JEP 444; JDK 25 does not newly stabilize them. A virtual thread is a java.lang.Thread that is not tied to one operating-system thread throughout its lifetime. The JDK schedules many virtual threads over a smaller set of platform threads.
This makes a thread-per-task programming style practical for many applications without requiring every task to occupy a platform thread while it waits. Existing code does not gain virtual threads merely by running on Java 25: an application or framework must create and use them.
What do virtual threads improve—and what do they not?
JEP 444 draws the important distinction: virtual threads are intended to provide “scale (higher throughput), not speed (lower latency).” They can help an application sustain more concurrent tasks when many tasks spend time waiting on I/O or other blocking operations. Whether that produces more throughput at an acceptable latency depends on the application and its constrained resources.
| Workload or goal | What to expect |
|---|---|
| Many concurrent requests waiting on I/O | Potentially greater concurrency and throughput, if the application, downstream services, and resource limits can support it. |
| CPU-bound computation | Virtual threads do not make the computation itself faster. Adding threads beyond available processor capacity does not create more CPU capacity. |
| Lower latency for one task | Not a general virtual-thread benefit; measure latency for the actual workload. |
Virtual threads are generally intended to be created per task rather than pooled as if they were scarce platform threads. They do not remove limits such as CPU capacity, memory, database or service capacity, connection pools, or other downstream constraints. Set appropriate resource limits and back-pressure, then measure before increasing concurrency.
What performance and concurrency changes does Java 25 add?
Java 25 includes changes with different aims. Some target concurrency programming, some startup or memory layout, and others diagnostics. None should be read as a guaranteed speedup for every application.
Rank #2
| Change | Status in JDK 25 | Purpose and practical scope |
|---|---|---|
| Virtual threads | Final since JDK 21 | Support high concurrency for tasks that often wait; not a general way to speed up CPU-bound work. OpenJDK JEP 444 |
| Scoped Values | Final in JDK 25 | Share immutable data through a bounded call chain and with child threads; useful for some context-sharing patterns. Oracle JDK 25 migration guide |
| Compact object headers | Product feature in JDK 25 | Reduce HotSpot object-header size on 64-bit architectures from 96 or 128 bits to 64 bits; potential heap, density, and locality benefits depend on object layout and workload. Oracle JDK 25 migration guide |
| AOT Command-Line Ergonomics and AOT Method Profiling | Available in JDK 25 | Simplify creating AOT caches and make method profiles from a prior run available at startup, helping the JIT compile earlier. These features target startup and warmup rather than guaranteeing higher steady-state throughput. Oracle JDK 25 migration guide |
| Java Flight Recorder (JFR) updates | Includes an experimental CPU-time profiling feature on Linux | Improve diagnostics: CPU-time profiling, more stable cooperative stack sampling with reduced safepoint bias, and method timing and tracing through bytecode instrumentation. These are investigation tools, not direct speedups. Oracle JDK 25 migration guide |
| Structured Concurrency | Preview API, fifth preview | Concurrency API still subject to preview status and possible change. Oracle JDK 25 release notes |
| Stable Values | Preview API | Preview feature, not a finalized API. Oracle JDK 25 release notes |
| Vector API | Incubator feature | Incubator feature, not a finalized API. Oracle JDK 25 release notes |
How do Scoped Values relate to virtual threads?
Scoped Values became final in JDK 25. They let a method make immutable data available to callees and child threads within a bounded scope. Oracle describes them as easier to reason about than thread-local variables and notes potential space and time advantages, particularly alongside virtual threads and structured concurrency. The JDK 25 migration guide explains the API change; Inside.java’s JDK 25 performance overview discusses sharing data without per-thread copies in relevant use cases.
Consider Scoped Values when data is immutable and should flow one way through a bounded call scope. They are not a drop-in replacement for every ThreadLocal: mutable state, lifetimes, or access patterns may make a different mechanism more appropriate. Structured Concurrency remains a preview API in JDK 25, so it has different stability implications from final Scoped Values.
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesWhat should you check before adopting virtual threads?
- Find the task boundaries. Identify where requests or independent tasks begin and end, and whether the work spends a meaningful share of its time waiting on I/O or other blocking operations.
- Inspect blocking and pinning behavior. JEP 444 describes cases where a virtual thread that blocks while executing synchronized code or native/foreign code can pin its carrier platform thread. Pay particular attention to frequent, long-lived pinning on important paths. Consult documentation for the exact JDK release you run; do not rewrite all synchronized code without evidence that a hot blocking path warrants it.
- Review thread-local assumptions. Check how much state is attached to ThreadLocal and whether any immutable, bounded context is a suitable Scoped Value use case.
- Check the whole stack. Confirm that frameworks, libraries, native calls, and observability tools behave as expected with virtual threads. Review whether thread-level metrics and traces remain useful for your operational needs.
- Protect scarce resources. Account for downstream service capacity, connection pools, memory, CPU, and other limits. Use limits and back-pressure where appropriate; a large number of available virtual threads does not mean every dependency can accept more work.
- Benchmark representative traffic. Compare the current JDK and JDK 25 with the same realistic workload. Measure throughput, latency distributions, CPU use, memory and heap, startup and warmup, and downstream saturation. Treat results as application-specific rather than inferring a percentage gain from the feature list.
For migration planning, use the JDK 25 migration guide and release notes to review compatibility and removed or deprecated items. Source, binary, and behavioral compatibility are distinct: compiling successfully alone does not establish that runtime behavior is unchanged.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Should you upgrade to Java 25?
Decide based on application compatibility, support policy, and measured results—not on virtual threads alone. The Java 25 feature set may be relevant if you need its finalized APIs, memory-layout change, startup and warmup options, or diagnostic capabilities. Preview and incubator APIs require a separate risk decision from finalized features.
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Oracle’s consolidated release notes list JDK 25.0.4.1 dated August 18, 2026. Patch availability, support terms, and update schedules vary by JDK vendor and can change, so consult your distribution’s current release notes and license terms before choosing a production update. Oracle consolidated JDK 25 release notes.
There is no general official percentage for how much Java 25 or virtual threads improve an arbitrary application. The 64-bit object-header reduction is a concrete runtime change, but its effect on a particular application depends on its object layout and workload. Likewise, startup, throughput, and diagnostic benefits require the matching use case.
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