Environment:Haifengl Smile Java 25 Runtime

Knowledge Sources	Smile Java 25 JDK
Domains	Infrastructure, JVM
Last Updated	2026-02-08 22:00 GMT

Overview

Java 25 JDK environment with Gradle 9.3.0 build system for compiling and running Smile v5.2.0.

Description

Smile v5.2.0 requires JDK 25 as the minimum Java runtime version. The project uses Java's Foreign Function & Memory API (Project Panama) for native library bindings to BLAS, LAPACK, and ARPACK. This requires the `--enable-native-access=ALL-UNNAMED` JVM flag. The build system is Gradle 9.3.0 with Java toolchain support. Tests require 6GB heap (`-Xmx6G`) with G1GC.

Usage

Use this environment for all Smile v5.2.0 development, compilation, and execution. JDK 25 is mandatory because the codebase uses `java.lang.foreign.*` APIs (Foreign Function Interface), pattern matching for switch expressions, and other modern Java features. Running with an earlier JDK will result in compilation or runtime errors.

System Requirements

Category	Requirement	Notes
OS	Linux, macOS, or Windows	Debian Trixie used in devcontainer
JDK	Java 25 (OpenJDK 25)	Configured via Gradle Java Toolchain
Build Tool	Gradle 9.3.0	Wrapper included in repository
Memory	6GB+ heap for tests	`-Xmx6G` required by test configuration
Disk	1GB+	For Gradle cache and build artifacts

Dependencies

System Packages

`openjdk-25-jdk` (or equivalent JDK 25 distribution)
`graphviz` (optional, for documentation generation)

Build System

`gradle` = 9.3.0 (via wrapper)
Kotlin plugin 2.3.0 (buildSrc)
Dokka 2.1.0 (documentation)

Core Java Dependencies

`org.slf4j:slf4j-api` = 2.0.17
`org.junit.jupiter:junit-jupiter` = 6.0.2 (test)

Credentials

No credentials required for the base Java runtime environment.

Quick Install

# Install JDK 25 (Ubuntu/Debian)
sudo apt update
sudo apt install -y openjdk-25-jdk

# Verify installation
java --version

# Build the project
./gradlew build

Code Evidence

Java 25 toolchain configuration from `buildSrc/src/main/kotlin/buildlogic.java-common-conventions.gradle.kts:18-21`:

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(25)
    }
}

Java 25 source/target compatibility from `buildSrc/src/main/kotlin/buildlogic.java-common-conventions.gradle.kts:32-35`:

tasks.withType<JavaCompile> {
    sourceCompatibility = JavaVersion.VERSION_25.toString()
    targetCompatibility = JavaVersion.VERSION_25.toString()
}

JVM flags for tests from `buildSrc/src/main/kotlin/buildlogic.common-conventions.gradle.kts:10-14`:

tasks.withType<Test>().all {
    jvmArgs("-Xmx6G", "-XX:+UseG1GC", "-XX:MaxMetaspaceSize=1024M", "-Xss4M")
    jvmArgs("--add-opens=java.base/java.nio=ALL-UNNAMED")
    jvmArgs("--enable-native-access=ALL-UNNAMED")
}

Foreign Function API usage in `base/src/main/java/smile/linalg/blas/cblas_h.java:5-6`:

import java.lang.invoke.*;
import java.lang.foreign.*;

Common Errors

Error Message	Cause	Solution
`UnsupportedClassVersionError`	Running with JDK < 25	Install and configure JDK 25
`java.lang.foreign not found`	JDK missing Foreign API	Ensure JDK 25 (not JRE) is installed
`OutOfMemoryError` during tests	Insufficient heap	Add `-Xmx6G` to JVM args
`InaccessibleObjectException`	Missing module opens	Add `--add-opens=java.base/java.nio=ALL-UNNAMED`

Compatibility Notes

JDK 25 is required: Earlier versions (JDK 21, 17, etc.) will not compile due to Foreign Function API and modern switch expression usage.
Kotlin targets JVM 25: Kotlin modules require JVM target 25 (`JvmTarget.JVM_25`).
Scala targets JVM 21: Scala modules use `--release:21` for compatibility.
Native access flag: The `--enable-native-access=ALL-UNNAMED` flag is mandatory for BLAS/LAPACK/ARPACK FFI calls.
DevContainer: A pre-configured devcontainer uses `mcr.microsoft.com/devcontainers/java:dev-25-jdk-trixie`.

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