JDK Versions & Distribution¶

Status: 🟢 Active  |  Owner: Java Guild

Current Standard¶

Approved Distribution¶

Eclipse Temurin (formerly AdoptOpenJDK) is the approved JDK distribution for all environments.

• Do not use Oracle JDK (licence restrictions).
• Do not use Amazon Corretto unless deployed exclusively on AWS Lambda (licence and support considerations).
• GraalVM Native Image is approved for specific use cases — requires Architecture Team sign-off.

Docker Base Images¶

Always use the Temurin slim variant:

# Runtime image
FROM eclipse-temurin:21-jre-alpine AS runtime

# Build image (multi-stage)
FROM eclipse-temurin:21-jdk-alpine AS builder

Never use the full JDK in the runtime stage of a Docker image.

Local Development¶

Use SDKMAN! to manage JDK versions locally:

sdk install java 21.0.3-tem
sdk use java 21.0.3-tem
sdk default java 21.0.3-tem

Pin the project version in .sdkmanrc:

java=21.0.3-tem

Commit .sdkmanrc to the repository. SDKMAN! will automatically switch to the correct version when entering the project directory.

CI Configuration¶

- uses: actions/setup-java@v4
  with:
    distribution: 'temurin'
    java-version: '21'
    cache: 'gradle'

Upgrade Policy¶

• Patch releases (21.0.2 → 21.0.3): Apply within 30 days.
• LTS to LTS (17 → 21): Required within 3 quarters of the new LTS becoming the standard.
• Non-LTS releases are not approved for production use.

Java 21 Features in Active Use¶

The following Java 21 features are approved and encouraged:

• Records — immutable data carriers, replacing POJOs.
• Sealed classes — closed type hierarchies, enables exhaustive switch.
• Pattern matching for instanceof — replaces verbose casting.
• Virtual threads (Project Loom) — available via Spring Boot 3.2+ configuration.
• Text blocks — multi-line strings.
• Switch expressions — expression form of switch.

References¶

• Eclipse Temurin releases
• SDKMAN!
• Java 21 Release Notes

Last reviewed: 2025-Q4  |  Owner: Java Guild