ptn1411/skill/java-decompiler

Claude Code and agent skill by ptn1411/skill

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Decompile Java applications (JAR/WAR/APK/class) — extract archives, detect obfuscators, decompile bytecode to source, analyse license logic and secrets.

Install

npx vskill@latest install ptn1411/skill/java-decompiler

SKILL.md

Java Decompiler

Purpose

Java bytecode (.class) retains nearly all source-level information, making decompilation highly effective. This skill extracts, decompiles, and analyses Java applications across all packaging formats: JAR, WAR, EAR, APK, and raw class files.

Workflow

┌──────────────────┐     ┌──────────────────┐     ┌──────────────────────┐
│ target.jar / .apk│────▶│ decompile_java   │────▶│ java-decompiled/     │
└──────────────────┘     └──────────────────┘     │  ├─ src/             │
                                │                  │  ├─ manifest.json    │
                                │                  │  └─ obfuscation.json │
                                ▼                  └──────────────────────┘
                         ┌──────────────────┐     ┌──────────────────────┐
                         │  analyze_java    │────▶│ java_analysis.json   │
                         └──────────────────┘     └──────────────────────┘

Usage

bash
# Decompile a JAR
python java-decompiler/scripts/decompile_java.py app.jar --out output/java-decompiled
 
# Decompile an Android APK
python java-decompiler/scripts/decompile_java.py app.apk --out output/java-decompiled
 
# Decompile with specific tool
python java-decompiler/scripts/decompile_java.py app.jar --out output/java-decompiled --decompiler cfr
 
# Analyse decompiled source
python java-decompiler/scripts/analyze_java.py output/java-decompiled --out output/java-analysis

Decompiler Priority

ToolBest forInstall
CFRGeneral JAR/class (best output quality)Download cfr.jar
ProcyonComplex generics, lambdasDownload procyon-decompiler.jar
FernFlowerIntelliJ-style outputDownload fernflower.jar
JADXAndroid APK (dex → java directly)pip install jadx or download
javapFallback bytecode listingIncluded with JDK

Outputs

FileContent
src/Decompiled .java source files
manifest.jsonParsed MANIFEST.MF + entry points
obfuscation.jsonDetected obfuscator + evidence
java_analysis.jsonLicense logic, secrets, endpoints, dependencies

When to use

  • binary-identifier reports Java language
  • Target is a .jar, .war, .ear, .apk, or .class file
  • Target contains META-INF/MANIFEST.MF or classes.dex

Anti-patterns

MistakeFix
Using only one decompilerCFR fails on some patterns → fallback to Procyon/FernFlower
Ignoring MANIFEST.MFContains Main-Class, classpath, version — always parse
Skipping obfuscator detectionDeobfuscate first (string decryption) for readable output
Treating APK as JARAPK uses DEX bytecode — needs dex2jar or JADX, not cfr directly
Missing inner classesInner classes are separate .class files — decompile the whole JAR

Security

  • Security scanPassed, 100 of 100Pattern checks on the skill's files.
  • Model reviewNot runA model review is scheduled for the next rescan.

See the full security report

Quality evaluation

  • Task evaluationNot runNo evaluation yet. Run one in Skill Studio.

See evaluation results

Source

Popularity

Repository stars
150
Repository forks
90
7-day trend score
25

Stars and forks are for the whole GitHub repository, not this skill alone. Not refreshed yet.

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