Question
What causes the java.lang.UnsupportedClassVersionError and how can I fix it?
Answer
The `java.lang.UnsupportedClassVersionError` typically indicates a version mismatch between the Java Runtime Environment (JRE) and the Java class files you are trying to run. This can happen if the Java class files were compiled with a newer version of Java than the runtime environment supports.
Causes
- The compiled .class files are created with a newer JDK version than the JRE version being used to run the application.
- The application may depend on libraries compiled with a higher version of Java.
Solutions
- Check the version of JDK used to compile the classes. You can do this using the command: `javac -version`.
- Ensure that you are running the application with a compatible JRE version. Use `java -version` to verify this.
- If using an IDE, configure it to use the correct JDK version in build settings or project settings.
- Consider upgrading your JRE to match the version of the JDK used for compilation.
Common Mistakes
Mistake: Running a class file compiled with Java 11 (version 55.0) on a Java 8 (version 52.0) runtime.
Solution: Ensure the JRE matches or exceeds the JDK version used to compile the class files.
Mistake: Forgetting to update environment variables after installing a new JDK version.
Solution: Make sure the `JAVA_HOME` and `PATH` are correctly set to the latest JDK.
Helpers
- java.lang.UnsupportedClassVersionError
- Java version mismatch error
- Java class file version error
- Unsupported class version
- Fix UnsupportedClassVersionError
