JEP 526: Simplifying Lazy Initialization in JDK 26

Honghao Wang

03 Dec 2025 — 2 min read

JEP 526 — Lazy Constants (Second Preview)

JEP 526: Lazy Constants has reached its second preview for JDK 26, following feedback from its first preview round (JEP 502: Stable Values).

Originally called Stable Values, this feature introduces computed constants — immutable value holders that are initialized at most once. They provide the performance and safety advantages of `final` fields, but with flexible initialization timing.

Why the Name Changed

The feature was renamed from Stable Values to Lazy Constants because:

It more clearly reflects their primary use case.
It improves discoverability for developers.
It signals a shift away from low-level control toward deferred, immutable computation.

---

Key API Changes

The previous Stable Values API allowed low-level operations:

These operations encouraged patterns contrary to the API’s intended purpose.

JEP 526 replaces them with a simpler class:

`java.lang.LazyConstant`

Supports only factory-based initialization via a `Supplier`.

---

Defining a Lazy Constant

A lazy constant is created with a supplier function.

The value is:

Computed once upon first access.
Cached permanently for subsequent use.

Example:

private static final LazyConstant LOG =
    LazyConstant.of(() -> Logger.create(MyService.class));

Usage:

void run() {
    LOG.get().info("service started");
}

This replaces older idioms such as:

Double-checked locking
Holder classes
Nullable fields

---

Advanced Usage — Lazy Lists and Maps

Lazy constants can be aggregated into lazy collections to defer creation of elements.

Lazy List Example

static final List ORDERS =
    List.ofLazy(POOL_SIZE, _ -> new OrderController());

OrderController controller() {
    long index = Thread.currentThread().threadId() % POOL_SIZE;
    return ORDERS.get((int) index);
}

Each element is created only on first access.
Same object returned on subsequent calls.

Lazy Map Example

static final Map ORDERS =
    Map.ofLazy(Set.of("Customers", "Internal", "Testing"),
               _ -> new OrderController());

OrderController controller() {
    return ORDERS.get(Thread.currentThread().getName());
}

Keys map to lazy constants.
Ideal for keyed pools or multi-tenant systems.

---

Notable Behavioral Changes

`null` values are disallowed.
Eliminates ambiguity, removes extra branching, and ensures a value is always present.
Philosophical shift:
From low-level synchronization + immutability (Stable Values)
➡️ High-level, everyday deferred initialization abstraction (Lazy Constants).

---

Performance and JVM Optimizations

When stored in a `final` field, a `LazyConstant` allows:

Defer expensive initialization until needed.
JVM constant folding after initialization.
Thread-safe access without manual synchronization.
Startup time reductions for applications with large graphs or costly resources.

---

Preview Status

Using Lazy Constants in JDK 26 requires:

`--enable-preview` during compilation.
`--enable-preview` during execution.

The development team is seeking feedback on:

API ergonomics
Naming conventions
Real-world applicability

If finalized, Lazy Constants will be a permanent Java language feature — replacing decades-old lazy-init idioms with a cleaner, optimized approach.

---

Content Creation & Multi-Platform Publishing Tip

For developers and technical writers covering topics like JEP 526, tools such as AiToEarn官网 can:

Generate AI-assisted articles & documentation.
Publish simultaneously to platforms: Douyin, Kwai, WeChat, Bilibili, Rednote, Facebook, Instagram, LinkedIn, Threads, YouTube, Pinterest, X (Twitter).
Integrate analytics and AI模型排名 tracking.
Monetize technical content while streamlining workflows.

Parallel with Lazy Constants:

Just as Lazy Constants optimize runtime resource usage, AiToEarn optimizes the creation and distribution cycle for technical content.

---

In summary:

Lazy Constants give Java developers:

Immutable, deferred initialization without boilerplate.
Thread safety by design.
JVM-level performance benefits.
If successful in preview, they will become a robust replacement for manual lazy-init patterns in modern Java.