Java Runtime Configurator

A Visual Studio Code extension that helps you discover Java runtimes and add them to the VS Code Java runtime configuration.

Requirements

• VS Code 1.100 or newer
• The Java extension reads and uses java.configuration.runtimes
• Access to the local filesystem where JDKs or JREs are installed

Command

• Java Runtimes: Scan Folders and Configure

What It Does

• Asks whether to scan common Java installation locations for your OS or choose one or more folders manually.
• Scans recursively for Java installations.
• Uses the detected Java version for the canonical execution environment name (for example, JavaSE-21).
• Adds a JSONC comment above each runtime entry with its kind, major version, vendor, and full version.
• Adds discovered Java homes to the java.configuration.runtimes setting.
• Adds sources and javadoc when those paths are detected.
• Prompts for which runtime should be the default for the current workspace and stores it in workspace settings.
• Repeated scans add new runtimes and refresh existing entries from their Java installations; existing workspace defaults are retained if selection is canceled.
• Shows folder and runtime counts while scanning, then lists versions and added/already-present status in the Java Runtime Configurator output channel.

How It Works

1. Run the command from the Command Palette.
2. Choose common OS installation locations or select one or more folders manually.
3. The extension searches recursively for directories that contain bin/java or bin/java.exe.
4. If javac is present, the runtime is treated as a JDK; otherwise it is treated as a JRE.
5. New runtimes are appended to java.configuration.runtimes in user settings.
6. You are prompted to choose which runtime should be the default for the current workspace.

Runtime Naming Rules

• The runtime name is a standard execution environment ID, such as JavaSE-18 (or J2SE-1.5 for Java 1.5).
• A comment above each runtime preserves descriptive details without adding unsupported properties to java.configuration.runtimes.
• If sources or javadoc are found, they are added to the runtime entry.

Example Workflow

1. Open the Command Palette.
2. Run Java Runtimes: Scan Folders and Configure.
3. Scan common locations (Oracle, Temurin, GraalVM, Azul, and Amazon Corretto), or select a folder such as /usr/lib/jvm or C:\Java.
4. Review the detected runtimes.
5. Choose the default runtime for the current workspace when prompted.

Example Settings

After selecting a workspace default, the workspace settings contain the complete runtime list with default set on the selected entry:

{
	"java.configuration.runtimes": [
		// [JDK 18] OpenJDK 18.0.2
		{
			"name": "JavaSE-18",
			"path": "/usr/lib/jvm/java-18-openjdk",
			"sources": "/usr/lib/jvm/java-18-openjdk/lib/src.zip",
			"javadoc": "/usr/share/javadoc/java-18-openjdk/api",
			"default": true
		}
	]
}

The entry is also added to user settings without default; sources and javadoc appear only when found.

Limitations

• The extension is intended for local filesystem runtimes.
• Common-location scanning checks existing standard vendor installation folders under Program Files on Windows, JavaVirtualMachines on macOS, and JVM/vendor folders on Linux. Use manual selection for nonstandard locations.
• Virtual workspaces are not supported.
• Existing runtime paths are retained, including paths that cannot be validated; valid installations have their runtime metadata refreshed on each scan.

Development

See DEV.md for prerequisites, development, local testing, packaging, and publishing.

Troubleshooting

• If no runtimes are found, verify the selected directory contains JDK or JRE installations with bin/java.
• If sources or javadoc are missing, verify the runtime installation includes lib/src.zip, docs/api, javadoc/api, or a matching shared javadoc directory.
• If packaging fails, run npm run compile first and confirm the repository is in a packageable state.

License

EPL-2.0