Why IDEA Fails to Start a Java Project with “error: java: invalid source release: 10”

Problem Background

After creating a new project, attempting to run it in IntelliJ IDEA produces the console error error: java: invalid source release: 10. The author identifies this as a JDK version mismatch problem.

Analysis

The machine has JDK 8 installed, but the IDEA project configuration points to JDK 10, which triggers the error. The author verifies the installed JDK by opening a CMD window and running java -version.

Solution Steps

Adjust the Java version used in the project structure (File → Project Structure…).

In the Project Structure dialog, select Project and ensure the Project SDK and language level match the installed JDK (e.g., JDK 8).

Open Settings → Build, Execution, Deployment → Compiler → Java Compiler and set the Per module bytecode version to the same JDK version as the system.

Verify the JDK version configured under File → Settings matches the installed JDK.

Inspect the project's pom.xml for the Java version configuration (e.g., <java.version>8</java.version> or the maven-compiler-plugin settings) and adjust it to the correct version.

After aligning the IDE, compiler, and Maven settings with the installed JDK, the project starts without the “invalid source release” error.

That concludes the discussion of the IDEA startup error.