How to Convert .class to .java: IntelliJ, Command Line, and Eclipse Methods

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Summary: Learn how to easily convert .class files to .java in IntelliJ, through the command line, and using Eclipse.
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Converting .class files back to .java files can be an essential task, especially when you need to inspect compiled Java bytecode or recover lost source code. In this guide, we will cover how to convert .class to .java in IntelliJ, from the command line, and in Eclipse.

Why Convert .class Files to .java?

Java .class files are compiled versions of .java source files, containing bytecode that can be executed on the Java Virtual Machine (JVM). However, there are specific scenarios where converting .class files back to .java is necessary:

Debugging purposes

Code review

Educational resources

Disaster recovery

Converting .class to .java in IntelliJ

IntelliJ provides integrated tools that make it easy to decompile .class files:

Open the .class file in IntelliJ.

Right-click on the file in the Project Explorer.

Select "View bytecode" or "Decompile" (depending on the IntelliJ version).

IntelliJ will decompile the bytecode and show you the approximate .java source file content.

Converting .class to .java via Command Line

The command line provides flexibility and speed for decompiling .class files:

Download and install a decompiler tool like JD-Core or CFR.

Open your terminal or command prompt.

Navigate to the directory containing the .class file.

Run the decompiler with the targeted file. For example, with CFR, use:

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The decompiled .java file will be displayed on the console or saved, depending on the tool’s configuration.

Converting .class to .java in Eclipse

Eclipse also supports decompiling .class files to .java through an integrated or third-party plugin. Here’s how:

Install a decompiler plugin like Enhanced Class Decompiler (ECD) from the Eclipse Marketplace.

Open the .class file in your Eclipse project.

The plugin will automatically decompile the bytecode and display the .java source code in the editor.

Conclusion

Whether you are using IntelliJ, the command line, or Eclipse, converting .class files back to .java is achievable with a few steps. Each method has its own sets of benefits: IntelliJ is integrated and user-friendly, command line offers flexibility and speed, and Eclipse provides a robust decompiling environment through plugins.

With these approaches, you'll have the tools you need to inspect or recover your Java source code efficiently.