Decompile Java — Class File

We’ve all been there. You inherit a legacy project with no source code, a critical dependency throws an unexplainable error, or a vendor goes out of business taking their documentation with you.

All you have is a .jar file (or a lone .class file). Is the code lost forever? decompile java class file

#!/bin/bash # decompile.sh JAR_FILE=$1 OUTPUT_DIR="./decompiled_src" unzip $JAR_FILE -d ./temp_classes Decompile all .class files find ./temp_classes -name "*.class" -type f | while read class; do java -jar cfr.jar "$class" --outputdir "$OUTPUT_DIR" done Clean up rm -rf ./temp_classes We’ve all been there

// Original public void process(int userId, String userName) ... // Decompiled (without debug symbols) public void process(int n, String s) ... Here’s a practical script to decompile a whole JAR using CFR: decompile java class file