Java Control Flow Flattener

Control flow flattening is a code obfuscation technique that transforms the natural branching structure of Java code (if-else, for, while, do-while, switch statements) into a flat switch-based dispatcher pattern. Instead of the JVM following the original branching logic, all code blocks are laid out as cases inside a master switch statement, and a state variable controls which block executes next. This effectively destroys the visible control flow graph, making static analysis and reverse engineering significantly more difficult.

1. Parse & Analyze: The tool scans your Java source code to identify all methods and their internal control flow structures - if/else branches, for loops, while loops, do-while loops, and switch statements.
2. Basic Block Extraction: Each identified control flow path is extracted into a labeled basic block. Simple statements become self-contained blocks, while nested control flow can be recursively flattened depending on the configured depth.
3. Dispatcher Generation: All basic blocks are reorganized into a master while(true) { switch(state) { ... } } structure. A state variable tracks which block to execute next, and each block updates the state before falling through.

• If/Else Branches: Each branch becomes a separate switch case with its own state assignment. Condition checks are preserved but obscured inside the dispatcher.
• For Loops: The initializer, condition check, increment, and body are split into separate switch cases, with state transitions controlling loop iteration flow.
• While & Do-While Loops: Transformed into state-based iteration where the condition is evaluated in a dedicated case and the state jumps to the body or exit accordingly.
• Switch Statements: Nested switch statements are either absorbed into the master dispatcher or transformed to use a separate state variable, depending on the selected flattening depth.

All processing is done entirely in your browser - your Java source code never leaves your device. Our Java control flow flattener uses a text-based transformation approach that works well for standard Java control flow patterns. For production-grade obfuscation, we recommend combining flattening with other techniques like identifier renaming and string encoding. Note that control flow flattening increases code size (each basic block adds dispatcher overhead) and may slightly reduce runtime performance due to the extra dispatching logic.