Resolving "Invalid source release: 17" IntelliJ Error

Problem Overview

The "Invalid source release: 17" error occurs when IntelliJ IDEA or Gradle cannot properly recognize or configure Java 17 as the target compilation version. This typically happens despite having Java 17 installed and configured in your project settings, creating frustration for developers transitioning from Java 8 or 11.

Root Causes

The error can stem from several configuration mismatches:

• Gradle using a different JVM than your project SDK
• Environment variables pointing to older Java versions
• Inconsistent Java version settings across project configuration files
• Multiple JDK installations causing conflicts

Comprehensive Solutions

1. Configure Gradle JVM in IntelliJ

The most common solution is to ensure IntelliJ's Gradle uses the correct JVM:

1. Open File → Settings (or IntelliJ IDEA → Preferences on macOS)
2. Navigate to Build, Execution, Deployment → Build Tools → Gradle
3. Under Gradle JVM, select your Java 17 installation
4. Click OK and rebuild your project

INFO

This setting ensures Gradle uses Java 17 for compilation, regardless of what JDK Gradle itself runs on.

2. Set Java Toolchain in Gradle

For a project-specific solution that works across all environments, configure the Java toolchain in your build.gradle:

build.gradle

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

build.gradle.kts

java {
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(17))
    }
}

TIP

The toolchain approach is preferred as it ensures consistent Java version usage across all development environments and CI/CD systems.

3. Verify Environment Variables

Check that your JAVA_HOME environment variable points to Java 17:

# Check current JAVA_HOME
echo $JAVA_HOME  # Linux/macOS
echo %JAVA_HOME% # Windows

# Set to Java 17 (example paths)
export JAVA_HOME=/path/to/jdk-17  # Linux/macOS
set JAVA_HOME=C:\path\to\jdk-17   # Windows

WARNING

After modifying environment variables, restart your terminal and IntelliJ IDEA for changes to take effect.

4. Check Project Structure Settings

Ensure consistency across IntelliJ's project settings:

1. File → Project Structure → Project

   • Set Project SDK to Java 17
   • Set Project language level to "17"

2. File → Project Structure → Modules

   • Verify Language level matches project settings
   • Confirm Module SDK is set to Java 17

3. Settings → Build, Execution, Deployment → Compiler → Java Compiler

   • Set Project bytecode version to 17

5. Clean Up Conflicting JDK Installations

Multiple JDK installations can cause conflicts:

1. Remove old JDK references from your system PATH environment variable
2. Delete obsolete Java installation directories
3. Check for and remove stale entries in ~/.gradle/gradle.properties:

# Remove or update any outdated Java home settings
org.gradle.java.home=/path/to/jdk-17

6. GitHub Actions Specific Configuration

If encountering this error in CI/CD pipelines, ensure proper Java setup:

- uses: actions/setup-java@v4
  with:
    distribution: 'temurin'
    java-version: '17'
    cache: 'gradle'

Additional Troubleshooting Steps

Verify JDK Consistency

Check that both java and javac commands use the same version:

java -version
javac -version

Both should report Java 17. If they differ, you have multiple JDK installations causing conflicts.

Check Run Configurations

For directly executed applications, verify run configurations:

1. Open Run → Edit Configurations...
2. Select your application configuration
3. Ensure JRE is set to your Java 17 installation

Clear Project and Gradle Caches

Sometimes cached data causes issues:

1. File → Invalidate Caches / Restart...
2. Delete the .gradle directory in your project root
3. Run ./gradlew clean build from terminal

Prevention Best Practices

1. Use Gradle Toolchains: Always specify Java version via toolchains in build files
2. Document JDK Requirements: Include JDK version in project documentation
3. Version Control IDE Settings: Consider committing .idea/misc.xml if team members use IntelliJ
4. CI/CD Configuration: Ensure build pipelines explicitly specify Java version

When Solutions Don't Work

If none of the above solutions resolve the issue:

1. Check for custom Gradle properties files that might override settings
2. Look for environment-specific configuration files
3. Verify no corporate or system-wide Gradle configuration files exist
4. Consider creating a new project and migrating code to isolate configuration issues

By systematically applying these solutions, you should be able to resolve the "Invalid source release: 17" error and successfully use Java 17 features in your IntelliJ projects.