Virtual File System (VFS) Simulation in Java 📁

A 100% Java-based project that simulates a hierarchical file system, demonstrating core Software Design Patterns to manage file and folder operations, including dynamic features like encryption and compression.

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✨ Features

• Hierarchical file and folder system
• Runtime file decoration (encryption, compression)
• Depth-First traversal of file system
• Clean separation using design patterns

🚀 Technical Highlights & Design Patterns

This project is structured around key object-oriented design patterns to ensure modularity, flexibility, and maintainability:

Structural Patterns

• Composite Pattern: Files (FileItem) and folders (FolderItem) are treated uniformly through the FileComponent abstract class, allowing the creation of a tree-like hierarchy.
• Decorator Pattern: The system dynamically adds responsibilities (e.g., encryption, compression) to files at runtime using EncryptedFile and CompressedFile decorators, without modifying the core file classes.

Behavioral Patterns

• Iterator Pattern: Implements the VFSIterator for traversing the entire file system hierarchy using a Depth-First Search (DFS) algorithm.

Simplification

• Facade Pattern: The FileSystemFacade simplifies complex system interactions (like moving files or creating deep structures) for the client code (Main.java).

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📂 Project Structure

SCD Lab Project/
│
├── src/vfs/
│   ├── Main.java                 # Application entry point and client demo
│   ├── FileSystemFacade.java     # Facade: simplifies high-level FS operations
│   ├── FileComponent.java        # Composite: base abstract class
│   ├── FileItem.java             # Composite: concrete leaf (regular file)
│   ├── FolderItem.java           # Composite: concrete composite (directory)
│   ├── FileDecorator.java        # Decorator: base abstract class
│   ├── EncryptedFile.java        # Decorator: adds encryption functionality
│   ├── CompressedFile.java       # Decorator: adds compression functionality
│   ├── VFSNode.java              # Interface for display/traversal
│   └── VFSIterator.java          # Iterator: custom DFS traversal
│
└── README.md

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🛠️ Getting Started

Prerequisites

• Java Development Kit (JDK) 8 or higher

Compilation and Execution

Compile the source files into a bin directory:

javac -d bin src/vfs/*.java

Run the compiled application:

java -cp bin vfs.Main

The program outputs the initial structure, demonstrates file movement, and shows the effects of decorators.

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🖥️ Demonstration Output

Initial File System:
+ root
   - hello.txt
   + Documents
      - notes.txt

After moving hello.txt to Documents:
+ root
   + Documents
      - notes.txt
      - hello.txt

Decorators Demo:
- (Encrypted) secret.txt
Decrypting secret.txt...
Opening decrypted file!

Opening compressed file:
Decompressing report.pdf...
Opening decompressed file!

Final File System:
+ root
   + Documents
      - notes.txt
      - hello.txt

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🗑️ File Deletion Demonstration

The system also supports deleting files through the FileSystemFacade..

Example usage in Main.java:

fs.deleteFile("/Documents/notes.txt");

Deleting notes.txt from Documents:
Deleted file: /Documents/notes.txt

After deleting notes.txt:
+ root
   + Documents
      - hello.txt

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💡 How to Extend This Project

• Add a new file type or decorator
• Create a new class extending FileDecorator (similar to EncryptedFile or CompressedFile)
• Implement display() and open() methods for the new behavior
• Apply the decorator to files in Main.java

Additional Enhancements

• Add more file system operations such as deleteFile(), renameFile(), or copyFile() in FileSystemFacade
• Enhance the iterator with BFS or file-type filtering
• Improve output formatting using icons or tags like [FOLDER] and [FILE]

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💻 Author

Aazain Jan

This project was created as part of my Software Construction & Development (SCD) coursework Fall 2025

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