Compile error "Class file has wrong version 52.0, should be 50.0"

Aligning IntelliJ IDEA and Java versions

Aligning the Java version used by your IDE and your codebase is essential. This avoids surprises when compiling. In IntelliJ IDEA, you need to manage the JDK used and the project-specific JDK:

1. Validate Project SDK: In File > Project Structure > Project Settings > Project, verify the Project SDK.
2. Align IntelliJ Compiler: In Build, Execution, Deployment > Compiler > Java Compiler, ensure your compiler's compatibility aligns with your Java version.

Compatibility with external libraries

External libraries or JAR files can also cause the mismatch. They should be compiled against the same Java version as your project:

• Examine JAR Versions: Check the version used to compile the JAR file. Tools like javap can help.
• Environment Variable: After changing Java versions, remember to update your JAVA_HOME.
• Maven Management: For Maven-based projects, specify the java.version in your pom.xml.

JDK and JRE: Consistent Configurations

Efforts to maintain identical JDK and JRE configurations across environments and within IntelliJ IDEA can prevent subtle version mismatch issues:

• Consistent JDK/JRE paths: Ensure the JDK and JRE paths match in environment variables and IntelliJ configurations.
• Additional JREs Config: You can specify alternate JREs for different run configurations in your project settings.
• Cross-Environment Checks: Validate JDK and JRE configurations across all environments where the code will be run.

Decoding class file versions

Java class file versions are represented by specific major version numbers:

• Java 6 maps to major version 50
• Java 8 maps to major version 52

A mismatch error occurs if your JAR file, for example compiled using Java 8 (major version 52), is loaded by a JVM operating on Java 6 (major version 50).