Java Learning Projects

A structured collection of Java console applications developed to build programming fundamentals. The repository progresses from basic syntax and logic to object-oriented programming, data structures, and external API integration. This project is part of Creativity, Activity and Service (CAS).

Most of these projects come from things I actually deal with or think about: robotics, electronics, food safety, and engineering math. Nothing here was built from a tutorial. Each project started as a problem like "how does Ohm's Law work on a breadboard?" or "can I simulate how a claw machine decides if you win?" and turned into working code.

Table of Contents

• Repository Structure
  • Simple Projects
  • Beginner Projects
  • Middle-Level Projects
• Concepts Applied
• How to Run (If you want i guess)
• Project Details
• References
• License

Repository Structure

The projects are organized by complexity into three main categories.

1. Simple Projects

Focused on basic I/O, control flow, loops, and math operations.

Project	Description	File
Basic Calculator	Performs addition, subtraction, multiplication, and division with formatted output.	Main.java
Number Guessing Game	Generates a random number between 1 and 100. Player has limited attempts with feedback.	Main.java
Ohm's Law Calculator	Calculates voltage, current, or resistance and checks if current levels are breadboard-safe.	Main.java
Age in Days Calculator	Converts age in years to days with leap year approximation and age-based messages.	AgeInDaysCalculator.java
Tip Calculator	Splits a bill among multiple people with tip percentage and input validation.	Main.java
Dice Roller	Rolls a die with a user-defined number of sides. Supports multiple rolls per session.	Main.java
Grade Point Averager	Averages grades across subjects and maps the result to a letter grade.	GradePointAverager.java
Mad Libs Generator	Prompts for word types and inserts them into a robot-maintenance themed story.	MadLibsGenerator.java
Motor RPM Estimator	Estimates theoretical and real RPM from KV rating and voltage, with linear speed output.	Main.java
Multiplication Table	Generates an N x N table with diagonal values highlighted in brackets.	Main.java
Odd/Even Checker	Checks if a whole number is odd or even using modulus.	Main.java
Palindrome Checker	Reverses and compares strings, ignoring spaces and case.	Main.java
Password Strength Checker	Scores passwords on length, character variety, and checks against a blacklist.	Main.java
Simple Login Prompt	Simulates login authentication with a 3-attempt lockout.	Main.java
String Reverser	Demonstrates both manual and StringBuilder string reversal side by side.	Main.java
Temperature Converter	Converts between Celsius and Fahrenheit with formatted decimal output.	TemperatureConverter.java
Vowel Counter	Counts the number of vowels in a user-provided sentence.	Main.java

2. Beginner Projects

Introduces arrays, regex, modular methods, timing, and basic state management.

Project	Description	File
Scientific Calculator	Command-driven calculator with trig, logarithms, roots, factorial, quadratic solver, memory, DEG/RAD mode, and history.	ScientificCalculator.java
Currency Converter	Converts between USD, EUR, and GBP using hardcoded exchange rates with cross-rate math.	Main.java
Unit Converter	Converts length, weight, and temperature units with optional scientific notation output.	UnitConverter.java
Book Catalog	Manages a catalog of books using parallel arrays with add, remove, search, and rate.	BookCatalog.java
To-Do List	Array-based task manager with priority levels and a robot-maintenance theme.	Main.java
Vending Machine Simulation	Full simulation with product browsing, coin insertion, greedy change-making, and a password-protected admin panel with sales reports.	VendingMachine.java
ATM Simulation	PIN-authenticated banking with deposit, withdraw, balance check, and attempt lockout.	Main.java
Study Timer	Pomodoro-style countdown timer with in-place console updates and bell alerts.	StudyTimer.java
Food Temperature Alert	Monitors temperature readings against safe ranges and generates summary reports.	FoodTemperatureAlertSystem.java
Claw Machine Drop Timer	Simulates drop timing using distance or X/Y coordinates with Pythagorean calculation.	ClawMachineDropTimer.java
Text Analyzer	Uses compiled regex patterns for word count, keyword search, and complexity analysis.	TextAnalyzer.java
Flowchart Syntax Generator	Generates valid Mermaid.js flowchart syntax from user input with label escaping.	Main.java
Flashcard Quizzer	Robotics safety themed quiz with scoring and a 100% pass gate.	FlashcardQuizzer.java
Random Workout Generator	Selects random exercises from four categories using ArrayList and Collections.shuffle.	RandomWorkoutGenerator.java
Rock Paper Scissors	Multi-round game with session stats and computer choice distribution tracking.	RockPaperScissors.java

3. Middle-Level Projects

Focuses on Object-Oriented Programming, file handling, external APIs, algorithms, and multi-file architecture.

Project	Description	Files
Robotics Component Inventory	File-based inventory system with CSV persistence, add/remove/search, and malformed line handling.	Component.java, InventoryManager.java, Main.java
Local Weather Dashboard	Fetches real-time weather data from the Open-Meteo API using HttpURLConnection with manual JSON parsing.	WeatherDashboard.java
Sorting Algorithm Visualizer	Console-animated comparison of Bubble Sort and Selection Sort with comprehensive performance metrics.	SortingVisualizer.java
Tic Tac Toe AI	Unbeatable AI opponent using the Minimax algorithm with depth-adjusted scoring.	TicTacToeAI.java
Manufacturing Assembly Line	Uses a Queue (LinkedList) as a FIFO conveyor belt with production simulation and quality control.	Product.java, AssemblyLine.java, Main.java
Automated Study Scheduler	Greedy scheduling algorithm that sorts subjects by priority and allocates hours across available days.	Subject.java, Day.java, Scheduler.java, Main.java
Expense Tracker	Logs expenses with category aggregation using LinkedHashMap.merge and saves formatted reports to file.	Expense.java, ExpenseTracker.java, Main.java
Claw Machine Arcade Tracker	Probability-based simulation with dynamic payout pressure that adjusts grip strength based on target payout rate.	Prize.java, Claw.java, GameSession.java, Main.java
Food Safety Database Logger	CRUD operations on temperature logs with danger zone analysis and ID-based lookup.	TempLog.java, FoodSafetyLogger.java, Main.java

Concepts Applied

Across these projects, the following Java concepts are utilized:

Core Java

• Variables, loops, conditionals, switch statements, and the Math class.
• Scanner for all user input with validation loops.
• DecimalFormat and printf for formatted numerical output.
• Thread.sleep for timing and console animation.

Object-Oriented Programming

• Classes with encapsulation, constructors, and getter methods.
• Immutable data models with final fields.
• Constructor injection for testability (Claw accepts a Random instance).
• Defensive programming with IllegalArgumentException on invalid inputs.

Data Structures

• Arrays and parallel arrays for simple data grouping.
• ArrayList for dynamic collections.
• LinkedList via the Queue interface for FIFO processing.
• LinkedHashMap with merge() for category aggregation.

File I/O and Serialization

• Reading and writing text files with FileWriter and BufferedWriter.
• File path management with java.nio.file.Path and Files.
• CSV-style persistence with line-by-line parsing and malformed line handling.

Networking

• HTTP GET requests with java.net.HttpURLConnection.
• URL encoding with URLEncoder and StandardCharsets.
• Manual JSON response parsing without external libraries.

Algorithms

• Minimax with depth-adjusted scoring for game AI.
• Greedy scheduling for resource allocation.
• Bubble Sort and Selection Sort with step-by-step visualization.
• Greedy change-making with denomination breakdown.
• Probability simulation with payout regulation.

Regex

• Compiled Pattern constants with word boundary matching.
• Matcher for keyword search and text complexity analysis.

How to Run (If you want i guess)

Make sure the Java Development Kit (JDK) is installed.

1. Clone the repository:

   git clone https://github.com/butunghd0-max/java-learning-projects-type-shyt.git

2. Navigate to the folder of the project you want to run.

3. Compile the Java file(s):

   javac Main.java

   Replace Main.java with the actual filename if it differs, e.g., StudyTimer.java.

   For multi-file projects, compile all files at once:

   javac *.java

4. Run the compiled class:

   java Main

Project Details

Quick usage notes for each project. Every project includes input validation, so expect clear error messages if you type something wrong.

Simple Projects

Basic Calculator - Enter two numbers and an operator. Handles division by zero and formats output to remove unnecessary decimals.

Ohm's Law Calculator - Choose which value to solve for (voltage, current, or resistance). After calculation, it checks if the current is safe for a breadboard (under 500mA warning, over 1A danger).

Motor RPM Estimator - Enter a motor's KV rating, voltage, and efficiency percentage. Outputs theoretical and real-world RPM. Optionally calculates linear speed from a wheel/propeller diameter. Warns if RPM exceeds 50,000.

Password Strength Checker - Checks length, uppercase, lowercase, digits, and special characters. Also runs the password against a blacklist of common passwords like "password123" and "qwerty".

Beginner Projects

Scientific Calculator - Type a command like sin, sqrt, quadratic, or pow and follow the prompts. Supports pi, e, mr (memory recall), and ans (last answer) as number inputs. Toggle between degrees and radians with mode. View past calculations with history.

Vending Machine Simulation - Browse products by category (Drinks, Snacks, Candy, Health) with stock labels. Insert coins/bills by denomination. The machine calculates change using a greedy algorithm and shows the exact coin breakdown. Admin mode (password: admin123) has sales reports, restocking, price changes, and low stock alerts.

Flowchart Syntax Generator - Follow the prompts to define flowchart steps. Outputs valid Mermaid.js graph TD syntax that you can paste into any Mermaid renderer.

Text Analyzer - Paste in text and get character count, word count, sentence count, average word length, and complexity classification. Search for keywords with regex word boundary matching.

Middle-Level Projects

Claw Machine Arcade Tracker - The simulation models real arcade machine behavior. The payoutPressure mechanic compares total money spent against the target payout rate and dynamically adjusts grip strength. Run 25 simulated plays and see win rate, money spent, and actual vs. target payout percentages.

Tic Tac Toe AI - Play against an unbeatable AI. The Minimax algorithm evaluates every possible board state. Depth-adjusted scoring means the AI prefers faster wins (scores 10 - depth instead of just 10).

Sorting Algorithm Visualizer - Generates a random array and visualizes Bubble Sort and Selection Sort step by step in the console using ANSI escape codes. Tracks outer loops, inner loops, comparisons, swaps, and total duration.

Local Weather Dashboard - Enter a city name. The program hits the Open-Meteo geocoding API to resolve coordinates, then fetches current weather data. JSON is parsed manually without any external library.

Robotics Component Inventory - Add, remove, update, and search components. Data persists to a local file between sessions. The Component class validates that names don't contain commas (which would break the CSV format).

Manufacturing Assembly Line - Products enter a Queue (conveyor belt), go through processing, and face a random quality control check. Failed products are rejected. Uses LinkedList implementing the Queue interface for FIFO behavior.

References

Cormen, Thomas H., et al. Introduction to Algorithms. 4th ed., MIT Press, 2022.

"Mermaid Flowchart Syntax." Mermaid, Mermaid Contributors, mermaid.js.org/syntax/flowchart.html. Accessed 22 Jun. 2025.

"Open-Meteo Geocoding API." Open-Meteo, open-meteo.com/en/docs/geocoding-api. Accessed 5 Nov. 2025.

"Open-Meteo Weather API." Open-Meteo, open-meteo.com/en/docs. Accessed 5 Nov. 2025.

Oracle. "Class HttpURLConnection." Java SE 21 API Specification, Oracle Corporation, docs.oracle.com/en/java/javase/21/docs/api/java.base/java/net/HttpURLConnection.html. Accessed 3 Nov. 2025.

Oracle. "Class Pattern." Java SE 21 API Specification, Oracle Corporation, docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/regex/Pattern.html. Accessed 15 May 2025.

Oracle. "Class Scanner." Java SE 21 API Specification, Oracle Corporation, docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/Scanner.html. Accessed 10 Dec. 2024.

Oracle. "Interface Queue<E>." Java SE 21 API Specification, Oracle Corporation, docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/Queue.html. Accessed 25 Jan. 2026.

Oracle. "Java SE Documentation." Oracle Help Center, Oracle Corporation, docs.oracle.com/en/java/javase/. Accessed 6 Dec. 2024.

Oracle. "Package java.nio.file." Java SE 21 API Specification, Oracle Corporation, docs.oracle.com/en/java/javase/21/docs/api/java.base/java/nio/file/package-summary.html. Accessed 18 Jan. 2026.

Russell, Stuart J., and Peter Norvig. Artificial Intelligence: A Modern Approach. 4th ed., Pearson, 2021.

License

This is a personal learning repository. Code is open for reference and educational use.