---

id: 49

slug: "stable-values"

title: "Stable values"

category: "concurrency"

difficulty: "advanced"

jdkVersion: "25"

oldLabel: "Java 8"

modernLabel: "Java 25 (Preview)"

oldApproach: "Double-Checked Locking"

modernApproach: "StableValue"

oldCode: |-

private volatile Logger logger;

Logger getLogger() {

if (logger == null) {

synchronized (this) {

if (logger == null)

logger = createLogger();

}

}

return logger;

}

modernCode: |-

private final StableValue<Logger> logger =

StableValue.of(this::createLogger);

Logger getLogger() {

return logger.get();

}

summary: "Thread-safe lazy initialization without volatile or synchronized."

explanation: "StableValue provides a lazily initialized, immutable value with built-in\

\ thread safety. No double-checked locking, no volatile fields, no synchronized\

\ blocks. The JVM can even optimize the read path after initialization."

whyModernWins:

- icon: "🧹"

title: "Zero boilerplate"

desc: "No volatile, synchronized, or null checks."

- icon: "⚡"

title: "JVM-optimized"

desc: "The JVM can fold the value after initialization."

- icon: "🛡️"

title: "Guaranteed once"

desc: "The supplier runs exactly once, even under contention."

support:

state: "preview"

description: "Preview in JDK 25 (JEP 502). Requires --enable-preview."

prev: "concurrency/scoped-values"

next: "concurrency/completablefuture-chaining"

related:

- "concurrency/virtual-threads"

- "concurrency/structured-concurrency"

- "concurrency/scoped-values"

docs:

- title: "Stable Values (JEP 502)"

href: "https://openjdk.org/jeps/502"

- title: "StableValue"

href: "https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/lang/StableValue.html"