If you’ve encountered the error message:
Class has been compiled by a more recent version of the Java Environment (class file version 53.0), this version of the Java Runtime only recognizes class file versions up to 52.0.This error occurs when your code has been compiled using a newer Java version than the Java Runtime Environment (JRE) currently running your application. In this case, your code was compiled with Java 9 (class file version 53.0), but your JRE supports Java 8 (class file version 52.0).
This post will explain what the error means and how to resolve it effectively.
Java Class File Versions
Each version of Java assigns a specific version number to the class files it compiles:
- Java 5 – version 49.0
- Java 6 – version 50.0
- Java 7 – version 51.0
- Java 8 – version 52.0
- Java 9 – version 53.0
- Java 10 – version 54.0
- Java 11 – version 55.0
- Java 12 – version 56.0
- Java 13 – version 57.0
- Java 14 – version 58.0
- Java 15 – version 59.0
- Java 16 – version 60.0
- Java 17 – version 61.0
- Java 18 – version 62.0
- Java 19 – version 63.0
- Java 20 – version 64.0
- Java 21 – version 65.0
In this example, Java 9 compiled the class file, but the project is running on Java 8. This results in a version mismatch.
The Root Cause
The error usually happens in the following scenarios:
- You compile your code with a higher version of the Java Development Kit (JDK), for example, Java 9, but attempt to run the code with a lower version JRE, such as Java 8.
- Your IDE (e.g., Eclipse) is set to use a higher JDK version for compilation but a lower JRE for execution.
In this case:
- Compiled with Java 9 (53.0)
- Running with Java 8 (52.0)
How to Fix This Error
1. Upgrade Your JRE to Match the Compilation Version
To run your code successfully, ensure that your JRE matches the Java version used during compilation. If your code was compiled with Java 9, upgrade your JRE to Java 9 or later.
Here’s how to do it:
- Download JRE 9 or later from the Oracle website.
- Install the JRE and configure your IDE (Eclipse) to use the new JRE.
2. Recompile Your Code with a Lower Version
If upgrading the JRE is not an option, you can recompile the code using Java 8 (JDK 8) so that it matches your existing JRE version.
In Eclipse:
- Go to Window > Preferences.
- Navigate to Java > Installed JREs and select JRE 8.
- Under Java Compiler, set the Compiler compliance level to 1.8.
- Rebuild the project.
Alternatively, if you are using Maven, update your pom.xml to specify the Java version:
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>3. Check Your IDE Configuration
If you’re using Eclipse (in this case, v4.7 Oxygen), ensure that both the JDK and JRE versions are set correctly.
- Configure JRE: Go to Window > Preferences > Java > Installed JREs and select the appropriate JRE.
- Configure JDK: Ensure the project’s Build Path is set to the JDK you want to use. Right-click on the project > Properties > Java Build Path > Libraries, and add the correct JDK version.
4. Use Multi-release JARs for Compatibility
If you need to maintain compatibility with multiple Java versions, consider using multi-release JARs. These JARs can contain different versions of classes for different Java versions, allowing you to run the same JAR on various versions of Java.
Conclusion
The version mismatch error occurs when your compiled code runs on a Java version lower than the one it was compiled for. The best solution is to match your JRE to the version used during compilation or recompile your code using the appropriate Java version. By following the steps above, you can resolve this issue and ensure compatibility across different Java environments.
This post focuses on helping users resolve common Java version mismatch issues and provides step-by-step solutions for fixing them in Eclipse or using Maven configuration.
