[Fixed] Unsupported Class File Major Version 61 in Java

1. Introduction

Java developers often face the challenge of compatibility issues, such as the unsupported class file major version 61" error. This problem arises when a Java program, compiled with Java 17 (denoted by major version 61), is run on a Java version that’s older than Java 17. This guide is crafted to be beginner-friendly and will walk you through various solutions to resolve this issue.

2. Understanding the Error

Unsupported class file major version 61 indicates a mismatch between the Java version used for compiling and running the program. Each Java version corresponds to a major version number (Java 17 is 61), and the Java Virtual Machine (JVM) expects compatibility between these versions during execution.

3. Comprehensive Solutions to Resolve the Error

3.1. Update the Java Runtime Environment (JRE)

Why It Works: Updating the JRE ensures that the Java version used to run the program matches or exceeds the version used for compiling it.
Steps:

• • Check Your Current Version:
    • Open a command prompt or terminal.
    • Type java -version.
  • Download and Install Java 17:
    • Visit the Oracle Java download page.
    • Choose the appropriate installer for your operating system and follow the installation steps.

• Verify the Update:
  • Run java -version again to check the new version.

3.2. Recompile the Java Program

Why It Works: Recompiling the program with a Java version that matches your runtime environment eliminates the version mismatch.

Steps:

• Install an Older JDK:
  • Download a JDK version that matches your runtime environment from the Oracle website.
• Recompile Your Program:
  • In the terminal, navigate to your program’s directory.
  • Use javac YourProgramName.java to recompile.
  • Run the program with java YourProgramName.

3.3. Change Project SDK in IntelliJ IDEA

Why It Works: IntelliJ IDEA might be using a different Java version for compiling your project.

Steps:

• Open Project Structure:
  • In IntelliJ, go to File > Project Structure.
• Adjust SDK:
  • In the Project section, change the Project SDK to Java 17 or the version you’re using.
• Rebuild the Project:
  • Use Build > Rebuild Project.

3.4. Update IDE and Plugins

Why It Works: Outdated IDEs or plugins might not support newer Java versions.

Steps:

• Check for Updates:
  • In your IDE, look for the option to check for updates (usually in the Help or File menu).
• Update:
  • Update the IDE and any Java-related plugins.

3.5.  Set Java Version in Andorid studio/Intellij Idea with gradle

if you are getting this issue with gradle in Android studio/Intellij IDE. You can follow below steps to resolve this.

• Go to Android Studio --> Preferences.
• Go to Build, Execution, Deployment --> Build Tools -->Gradle.
• Change the Java version to either Android Studio default JDK or Embedded JDK.
  

You can also try to upgrade the gradle version to fix this issue.

3.6. Configure Build Tools

Why It Works: Specifying the Java version in build tools like Maven or Gradle ensures consistency during compilation.
For Maven (pom.xml):
Set the Java version for maven in the maven-compiler-plugin configuration.

For Gradle (build.gradle):
Use sourceCompatibility and targetCompatibility to specify the Java version in gradle.

3.7. Use jdeps for Compatibility Analysis

jdeps is a command-line tool included in the JDK that analyzes Java class files and determines their dependencies, including which version of Java they require. This can be particularly useful when you’re trying to understand the compatibility of various parts of your application.

How to Use jdeps:

• Check if JDK is Installed:
  • Ensure you have the JDK installed as jdeps comes with it. You can verify this by typing java -version and javac -version in your command prompt or terminal.
• Run jdeps on Your Java File or JAR:
  • Open the command prompt or terminal.
  • Navigate to the directory where your Java file or JAR file is located.
  • Run jdeps with the name of your Java file or JAR file. For example, jdeps MyProgram.jar or jdeps MyProgram.class.
• Analyze the Output:
  • jdeps will output information about the dependencies of your Java file or JAR, including which version of Java they require.
  • Look for lines indicating dependencies on specific Java versions. This will help you understand the minimum Java version required to run your program.
• Decide on the Next Steps:
  • If jdeps shows dependencies that require a newer Java version than what you have, consider updating your Java version.
  • If updating Java isn’t possible, try to modify your code or change dependencies to be compatible with your current Java version.

Example of Using jdeps:

Suppose you have a file named MyProgram.class. In your terminal, you would run:

This command will give you a detailed output about the class file, including the Java version required by each dependency it has.

3.8. Use Tools for Compatibility

Sometimes, you can use certain tools to make your Java class files compatible with older Java versions. A popular tool for this purpose is Javac with the --release option. This tool allows you to compile your Java programs for a specific Java version.

Steps:

• Install the Latest JDK:
  • First, ensure you have the latest JDK installed. You can download it from the Oracle Java download page.
• Recompile Your Program for an Older Java Version:
  • Open the command prompt or terminal.
  • Navigate to your Java program’s directory.
  • Use the Javac tool with the --release option followed by the target Java version. For example, if you want to compile for Java 11, use javac --release 11 YourProgramName.java.
• Run Your Program:
  • Now, try running your program again using java YourProgramName.

This method allows you to create a Java program compatible with older versions without needing to install those versions.

3.9. Configure Environment Variables

Why It Works: Correct environment variables ensure that the system uses the intended Java version.

Steps:

• Set JAVA_HOME:
  • Make sure JAVA_HOME points to the JDK directory.
• Update PATH:
  • Add the JDK bin directory to your PATH environment variable.

3.10. Use SDKMAN! for Java Version Management

Why It Works: SDKMAN! allows easy switching between different Java versions.

Steps:

• Install SDKMAN!:
  • Visit SDKMAN!’s website and follow the installation instructions.
• Switch Java Versions:
  • Use sdk list java and sdk use java <version> to switch between Java versions.

3.11. Create a Fat Jar with Dependencies

Creating a fat jar, which includes all dependencies, makes your application more versatile and less dependent on the environment.

Using Maven:

• Edit pom.xml:
  • Add the maven-assembly-plugin configuration to your pom.xml.
• Build the Fat Jar:
  • Run mvn clean compile assembly:single in your project directory.

Using Gradle:

• • Edit build.gradle:
    • Include the necessary configuration for creating a fat jar in your build.gradle.
  • Build the Fat Jar:
    • Execute gradle build to create the jar.

4. Conclusion

The “unsupported class file major version 61” error in Java is a common issue that stems from version incompatibility. By updating your Java version, recompiling the program, using an IDE, employing compatibility tools, creating a fat jar, keeping your IDE up-to-date, or managing versions with SDKMAN!, you can efficiently resolve this error. Each method offers a way to align your development environment with the Java version requirements of your project, ensuring smooth operation and execution of your Java applications.