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📂 Repository Overview

Welcome to the Algo-Lab: Core Java Fundamentals & Python Ports repository. This project is a curated, production-grade library of core algorithmic implementations, mathematical theorems, string manipulations, array optimizations, and object-oriented design patterns.

Originally built as a collection of standalone Java files, this repository has undergone a complete code audit, structural reorganization, and refactoring. The repository now features:

1. Refactored & Package-Grouped Java Source Code (com.corejava.*): Cleaned of all syntax errors, infinite loops, typos, and bad exception handling.
2. Parallel Production-Grade Python Port (utils/*): Fully type-annotated, document-guided, PEP 8 compliant, and safe against edge cases (division by zero, negative bounds).
3. Interactive Command-Line Interface (main.py): A central, unified terminal menu providing seamless access to run all ported algorithms and verify logic.
4. Diagnostic Unit Test Suite (tests/*): Over 45 assertions covering typical inputs, edge cases, and error states using Python's built-in unittest library.

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🧠 Repository Directory Tree

Below is the flattened, logically structured codebase organization:

core-java-main/
├── java/
│   └── src/
│       └── com/
│            └── corejava/
│                 ├── array/          # PalindromeArray, ArrayMax, ArrayLen, ArrayEven, Array
│                 ├── file/           # Folder
│                 ├── geometry/       # Circle, Rect, Tria, Areas
│                 ├── math/           # Disarium, Duck, HappyNumber, NeonNumber, Niven, Prime, etc.
│                 ├── oop/            # Child, MyClass
│                 └── string/         # Ascii, Count, ExtractStr, FindString, Palindrome, etc.
├── utils/                            # Python Production-Grade Ports
│   ├── __init__.py
│   ├── array_utils.py                # List processing, min/max, primes filters
│   ├── file_utils.py                 # Directory creation
│   ├── geometry_utils.py             # Shape areas and perimeters
│   ├── math_utils.py                 # Mathematical and number theory algorithms
│   ├── oop_demos.py                  # Abstract classes, inheritance, simple interest
│   └── string_utils.py               # Palindromes, ASCII converter, title case toggles
├── tests/                            # Diagnostic Unit Tests
│   ├── __init__.py
│   ├── test_array.py
│   ├── test_geometry.py
│   ├── test_math.py
│   ├── test_oop.py
│   └── test_string.py
├── assets/                           # SVG Badge Elements & Graphics
│   ├── title_banner.svg
│   └── stats_dashboard.svg
├── .gitignore                        # Cache, class files, and IDE exclusions
├── LICENSE                           # MIT Open-Source License
├── main.py                           # Unified CLI Menu & Entrypoint
└── README.md                         # Main Project Documentation

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🔍 Code Audit & Bug Resolution Log

A deep analysis of the legacy codebase uncovered several compile-time and runtime bugs. The table below outlines these findings and their resolutions:

#	Filename	Bug Type	Description	Resolution
1	Name.java	Syntax & Logic	else block placed after the loop; comparison b == 'a' checks integer index against character code; missing return statement.	Rewrote analyze_name to safely verify string boundaries using standard startsWith and endsWith methods, and added correct returns.
2	Xyz.java	Syntax	else block placed after the loop; method upper lacks default return statement when character range isn't matched.	Re-implemented as check_alphabets with a correct loop, boundary checks, and standard default return statements.
3	getSubstring.java	Syntax & Logic	else block placed after the loop; parameters not passed; method returns original string instead of substring.	Re-implemented as GetSubstring with package parameters getSub(String, int, int) and bound-safe slicing.
4	TitleStr.java	Syntax	Undeclared variables s and i; non-existent method toCharAt; lacks return statement.	Rewrote as TitleStr.toTitleCase with standard camel-casing logic and loop checks.
5	FindString.java	Runtime (Infinite Loop)	Inner loop for (int j = 0; i < string2.length(); i++) increments outer index i instead of j, creating infinite loops.	Fixed to use Java's standard string2.contains(string1) for clean, O(N) substring checking.
6	FindSub.java	Runtime (Infinite Loop)	Inner loop checking condition uses i but increments j and indexes with j, resulting in out-of-bounds or infinite loops.	Simplified to use Java standard substring checker.
7	special.java	Logic	Loop resets fact = 0; at the end of each digit's iteration. For subsequent digits, fact = a * 0 results in zero factorial sum.	Corrected the reset value to fact = 1; at the start of each digit's factorial evaluation loop.
8	PalindromeNum .java	Syntax & Structure	Extra closing brace at the end of the file; trailing whitespace in the filename itself.	Renamed file to PalindromeNum.java, removed extra brace, and cleaned up indentation.
9	provic.java	Logic & Naming	Typos in terminology ("provic" instead of "pronic"); redundant outer loop that does not use iteration index i.	Renamed file to Pronic.java and replaced redundant loop with a clean square-root bound check n * (n + 1) == num.
10	Home.java	Name Conflict & Logic	Shared the class name Home with areas.java causing class compilation collisions. Pronic divisor logic was incorrect.	Deleted duplicate class name and merged the pronic checking logic into Pronic.java.
11	ArrayLen.java	Logic & Usability	Allocates array but never reads elements, leaving them all default 0. Prints string literal "a1" instead of values.	Fixed array input scanner loop and updated check to identify and print actual prime numbers.
12	Circle.java	Type Mismatch	Defined radius r as a float but read input using nextInt(), crashing on decimal inputs (e.g., 5.5).	Updated radius scanner to nextFloat() and added radius sign check.
13	Array.java	Arithmetic (Div by Zero)	In case of size n = 0, integer division sum / n throws ArithmeticException.	Protected division by requiring positive array sizes, and cast to double for fractional average accuracy.
14	Even.java	Output Clutter	Printed running sum values inside the loop at every iteration, cluttering console output.	Moved print statements outside of the range loop, printing only the final sums.
15	ArrayEven.java	Logic & Naming	Outputs the single array element while naming it "the sum of even".	Refactored output to show separate itemized prints and compute actual sums.
16	Folder.java	Typos & Exception Handling	Typo "foider created..."; bare catch clause printed raw exception without details.	Fixed typos and added specific security exception messaging.
17	TitleCase.java	Out of Bounds	Space checks at the end of the string trigger s.charAt(i+1) which throws StringIndexOutOfBoundsException.	Handled string index checks safely with string bounds limits.
18	Power.java	Logic	Swapped input variables (base and exponent read in reversed order).	Standardized input reading order: base then exponent.
19	PrimeRan.java	Logic	Identical duplicate of Prime.java checking a single number instead of executing a range print.	Re-implemented to accept start and end bounds and print all primes in that range.

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🛠️ Environment Setup Instructions

To set up your local development environment for running both Python and Java programs:

1. Python Environment Setup

1. Verify Python Installation: Ensure Python 3.10 or higher is installed:

   python --version

2. Create a Virtual Environment: It is recommended to use a virtual environment:

   python -m venv .venv

3. Activate the Virtual Environment:
   • Windows (PowerShell):

     .venv\Scripts\Activate.ps1

   • Windows (Command Prompt):

     .venv\Scripts\activate.bat

   • macOS / Linux:

     source .venv/bin/activate

2. Java Environment Setup

1. Install Java Development Kit (JDK): Ensure JDK 8 or higher is installed.
2. Configure Environment Variables:
   • Set the JAVA_HOME environment variable pointing to your JDK installation directory (e.g., C:\Program Files\Java\jdk-17).
   • Add the JDK binary path (e.g., %JAVA_HOME%\bin on Windows or $JAVA_HOME/bin on macOS/Linux) to your system PATH variable.
3. Verify Java Compiler Installation:

   java -version
   javac -version

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🚀 Running the Project

Python Entry Point & CLI Menu (Recommended)

To run the interactive menu to execute algorithms, OOP demos, or file tools:

python main.py

Running Automated Python Tests

To run the unit test suite with verbose summary outputs:

python -m unittest discover -s tests

Alternatively, you can select option 7 in the interactive menu run by main.py.

Compiling & Running Java Source Files

To compile and run any of the Java source files, navigate to the java/src/ folder:

cd java/src
javac com/corejava/math/Disarium.java
java com.corejava.math.Disarium

(Note: Ensure you have JDK 8+ installed and added to your environment variables to compile Java classes.)

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📄 License & Standards

• License: Released under the standard MIT License.
• Python Quality: Strictly formatted to follow PEP 8 guidelines (4-space indentations, camel-cased classes, snake-cased variables, clear type annotations, and docstrings).
• Language: All code logs, console print statements, comments, and document files are written in standard, professional English.

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⭐ Give a Star!

If you find this repository helpful for your studies or code practices, please show your support by giving this repository a star! It helps others discover the project.

1. Go to the top right of the GitHub repository page.
2. Click the Star button.

Thank you!