Java From Scratch With DSA

Hands-on Java and DSA practice through small, single-topic programs.

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🔍 What You'll Learn

• Syntax and operators
• Control flow (if/else, loops)
• Methods and parameter passing
• OOP essentials (classes, objects, inheritance, interfaces, abstract classes)
• Collections basics (arrays, ArrayList, Vector, Stack)
• Exception handling and basic I/O
• Recursion and pattern-printing exercises

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💻 Technologies & Tools

• Java (JDK 17+)
• Any IDE or text editor (e.g. VS Code, IntelliJ IDEA, Eclipse)
• Command line / Terminal

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🚀 Getting Started

1. Clone the repository:

   git clone https://github.com/debug-node/Java-from-scratch.git

2. Navigate into the project folder:

   cd Java-from-scratch

3. Compile and run Java files. Since the project uses standard Java package structures, compile from the repository root specifying a directory for class files, then run using the fully qualified package class name:

   # Compile to an 'out' output directory
   javac -d out basic/simple/HelloWorld.java
   
   # Run using class path and package name
   java -cp out basic.simple.HelloWorld

4. Alternatively, to run any package file directly via java (on modern JDKs supporting single-file execution, but note package structure constraints):

   java basic/simple/HelloWorld.java

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📁 Reorganized Project Structure

The workspace has been organized into clean, categorized, and consistent directories using standard Java package naming and formatting conventions:

Java-from-scratch/
├── basic/                     # Basic Java syntax and fundamentals
│   ├── simple/                # Basic templates, greetings, conversions
│   ├── operators/             # Arithmetic and logical operators
│   ├── conditions/            # Conditional logic exercises
│   ├── loops/                 # Iterations, pallindromes, tables
│   └── functions/             # Modular reusable methods
│
├── datastructures/            # Fundamental data structures
│   ├── arrays/                # Linear arrays, search and max/min
│   ├── arraylists/            # ArrayLists, Vector, Stack practices
│   └── strings/               # String manipulation algorithms
│
├── algorithms/                # Algorithmic concepts
│   ├── patterns/              # Pyramids, butterlies, and grid prints
│   └── recursion/             # Recursion, fibonacci, and factorials
│
├── oop/                       # Object-Oriented Programming principles
│   ├── classesobjects/        # Classes, object instantiation, rectangle calculations
│   ├── inheritance/           # Code reuse, final methods/classes, super calls
│   ├── abstractclasses/       # Abstract templates and specific behaviors
│   ├── interfaces/            # Implementing interface methods and abstractions
│   ├── caloriescalculator/    # Multi-class calories calculator program
│   └── grades/                # Grades-calculation classes
│
├── exceptionhandling/         # Exception handling, try-catch, custom/user exceptions
│
├── packages/                  # Java custom packaging and access controls
│   └── mypack/
│
└── assignments/               # Banking, multi-threading, and general calculator systems

Tip: View the live tree anytime (Windows):

tree /F /A

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✅ How to Contribute / Use It

• Try writing small Java programs using concepts learned
• Feel free to add your own examples or exercises
• If you find bugs or improvements, submit pull requests

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Badges

• JDK 17+
• PRs welcome

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🧑‍💻 Author

• debug-node