Try to invoke main class org.jetbrains.java.decompiler.main.decompiler.ConsoleDecompiler manually

java -cp java-decompiler.jar org.jetbrains.java.decompiler.main.decompiler.ConsoleDecompiler myclassfile.class .

Also you can find more about internal usage of Fernflower inside IDEA by query in source code https://github.com/JetBrains/intellij-community/search?utf8=%E2%9C%93&q=Fernflower

Answer from qwazer on Stack Overflow
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GitHub
github.com › JetBrains › fernflower
GitHub - JetBrains/fernflower: Decompiler from Java bytecode to Java, used in IntelliJ IDEA.
The Fernflower IDE plugin is bundled in IntelliJ IDEA. Open any .class file and you should see the decompiled Java source code: this is Fernflower in action. The plugin is also open-source and can be found here. java -jar fernflower.jar [-<option>=<value>]* [<source>]+ <destination>`
Starred by 4.1K users
Forked by 715 users
Languages   Java
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Bytecode
the.bytecode.club › showthread.php
FernFlower - CLI Java Decompiler
July 17, 2014 - java -jar fernflower.jar -ren=1 jarToDecompile.jar decomp/ For more options, read the FernFlower documentation here.
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Maven Repository
mvnrepository.com › artifact › org.jboss.windup.decompiler › decompiler-fernflower › 2.3.0.Final
Maven Repository: org.jboss.windup.decompiler » decompiler-fernflower » 2.3.0.Final
Home » org.jboss.windup.decompiler » decompiler-fernflower » 2.3.0.Final · Windup Engine Decompiler Fernflower · Note: There is a new version for this artifact · Maven · Gradle · SBT · Mill · Ivy · Grape · Leiningen · Buildr · Scope: compile · test · provided ·
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Reddit
reddit.com › r/java › new open source java decompiler
r/java on Reddit: New open source Java decompiler
April 29, 2022 -

Hello! Today I'm happy to announce the release of a project that me and my friends have been working on over the course of the last year, Quiltflower! Originally intended just for use with the QuiltMC toolchain with Minecraft, Quiltflower quickly expanded to be a general purpose java decompiler aiming to create code that is as accurate and clean as possible. If the name sounds familiar it's because Quiltflower is a fork of Fernflower, the (in)famous decompiler that was developed by Stiver, maintained by Jetbrains, and became the default decompiler in Intellij IDEA. Fernflower also quickly found its way into many other tools. After many frustrations with it myself with its decompiled code structuring and quality I decided to do something about it, and here we are! Over the past year, Quiltflower has added support for features such as modern string concatenation, a code formatter, sealed classes, pattern matching, switch expressions, try-with-resources, and more. Quiltflower also focuses on the code quality of the decompiled output, and takes readability very seriously. We'd greatly appreciate it if you'd give it a try, with our Intellij Plugin, as a standalone jar, or on our maven. While it has come a long way it's still a work in progress, and feedback can be reported on our issue tracker.

Here's a comparison of Fernflower and Quiltflower's output.

I'd also like to thank the MinecraftForge Team for creating ForgeFlower, the fork that QuiltFlower was based on, and Lee Benfield for creating CFR and it's truly incredible test suite.

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npm
npmjs.com › package › fernflower
fernflower - npm
A fernflower <jarFile> <outputDir> cli can be installed with npm install -g fernflower ·
      » npm install fernflower
    
Published   Apr 01, 2016
Version   1.1.0
Author   Romain Beaumont
Find elsewhere
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SoftTeco
softteco.com › home › java development › fernflower java decompiler
Fernflower Java Decompiler
July 3, 2025 - Fernflower is a really nice Java decompiler. It’s pretty convenient since you can decompile the whole JAR file.
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GitHub
github.com › fesh0r › fernflower
GitHub - fesh0r/fernflower: Unofficial mirror of FernFlower Java decompiler (All pulls should be submitted upstream)
The Fernflower IDE plugin is bundled in IntelliJ IDEA. Open any .class file and you should see the decompiled Java source code: this is Fernflower in action. java -jar fernflower.jar [-<option>=<value>]* [<source>]+ <destination>`
Starred by 3.8K users
Forked by 699 users
Languages   Java
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JetBrains
youtrack.jetbrains.com › issue › IDEA-175638 › Please-release-fernflower-decompiler-as-a-standalone-jar
Please release fernflower decompiler as a standalone jar
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YouTube
youtube.com › watch
How to create fernflower JAR and decompile Kotlin class to Java using a command line? - YouTube
fernflower is used internally by Intellij IDEA as a decompiler. If you have a use case to decompile Kotlin classes to Java using the command line, this video...
Published   April 21, 2021
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GitHub
github.com › wux1an › fernflowers
GitHub - wux1an/fernflowers: Java ☕ reverse engineering tool - Batch decompile the jar package.
So I developed this program based on fernflower to optimize these problems, with the following features ... usage: java -jar fernflowers.jar [args] -h,--help help -i,--input <arg> input, the directory to be scanned or a single file path.
Starred by 10 users
Forked by 4 users
Languages   Java
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YouTube
youtube.com › wernerware
Fernflower Decompiler for Java - YouTube
Use Fernflower to decompile java code from .class and .jar files. This video shows you how to do it without IntelliJ Video notes: https://github.com/wernerwa...
Published   June 16, 2018
Views   5K
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Mkyong
mkyong.com › home › java › how to decompile class in java
How to decompile class in Java - Mkyong.com
July 1, 2021 - # decompile JAR or Class files # java -jar fernflower.jar /path/asm-analysis-3.2.jar /path/unknown.class /path/decompile/ $ java -jar fernflower.jar /path/asm-analysis-3.2.jar /path/decompile/ INFO: Decompiling class org/objectweb/asm/tree/...
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JetBrains
youtrack.jetbrains.com › issue › IDEA-332138
Bug while decompiling a jar file using standalone fernflower.jar
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Maven Central
central.sonatype.com › artifact › org.jboss.windup.decompiler › decompiler-fernflower › 6.3.1.Final
decompiler-fernflower - Maven Central - Sonatype
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.jboss.windup.decompiler</groupId> <artifactId>decompiler-parent</artifactId> <version>6.3.1.Final</version> </parent> <artifactId>decompiler-fernflower</artifactId> <name>Windup Engine - Decompiler Fernflower</name> <dependencies> <!-- Local Dependencies --> <dependency> <groupId>org.jboss.windup.d
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Jar-download
jar-download.com › artifact-search › decompiler-fernflower
Download decompiler-fernflower JAR file with all dependencies
January 17, 2023 - Download decompiler-fernflower JAR file ✓ With dependencies ✓ Documentation ✓ Source code
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Jar-download
jar-download.com
Download fernflower JAR files with all dependencies
Download JAR files for fernflower ✓ With dependencies ✓ Documentation ✓ Source code