🔸 TLDR
Project Valhalla aims “to align JVM memory layout behavior with the cost model of modern hardware.”
Its key idea: introduce data that can behave like composite objects without object identity, reducing overhead and opening the door to deeper Java evolution.
Here are 5️⃣ quotes from Ben Evans that capture why Valhalla matters. 👇
1️⃣ THE SCALE OF VALHALLA
“It is probably the most ambitious project ever conducted within OpenJDK.”
This is much deeper than a language feature: JVM, libraries and Java’s type system are affected.
#OpenJDK
2️⃣ JVM OPEN-HEART SURGERY
“It is effectively open-heart surgery on the JVM.”
Valhalla touches the foundations of Java’s object model while preserving compatibility with a mature ecosystem.
#JVM
3️⃣ THE CORE IDEA
“What if there was a new kind of data - one which represented composite or user-defined data types, but which did not have identity?”
Value classes bring object-like structures without paying for identity when identity is unnecessary.
#ValueClasses
4️⃣ BEYOND VALUE CLASSES
“Valhalla opens the possibility that the Java language designers can use this singular opportunity to undertake work that was previously believed to be intractable”
Think generics, primitive/object unification and potentially nullability markers in the type system.
#JavaLanguage
5️⃣ VALHALLA HAS LANDED
“The first pieces of Valhalla have, at long last, landed on OpenJDK main as Preview Features.”
JDK 28 EA makes Valhalla accessible to a much broader group of Java developers for real-world experimentation.
#JDK28
🔸 TAKEAWAYS
▪️ Valhalla introduces identity-free composite data through value classes.
▪️ It can reduce object-header and indirection costs.
▪️ Existing JDK classes are already being migrated experimentally.
▪️ Its impact could eventually reach generics, nullability and the primitive/object divide.
▪️ The next challenge is ecosystem compatibility: Gradle, Kotlin, ASM and other tooling still need to catch up.
As Ben puts it, Valhalla is “a truly extraordinary achievement” involving “root-and-branch change in a stable, mature, best-in-class general purpose ecosystem.”
Now that the first pieces are landing: watch this space for updates. 👀
#Java #ProjectValhalla #OpenJDK #JVM #JDK28 #ValueClasses #JavaDevelopment #SoftwareEngineering
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