SaiKet Systems | Java Internship Program

Building Real-World Java Applications with Core Java, OOP, File Handling & Software Design

☕ Java Project Portfolio

Successfully Completed During the SaiKet Systems Java Training Program

👨‍💻 AMIT KUMAR MAITY

Java Developer | Software Engineering Student | Open Source Enthusiast

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💡 From Java Fundamentals to Advanced Object-Oriented Programming

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📌 About This Repository

This repository contains six complete Java console applications developed as part of the SaiKet Systems Java Training Program.

The projects demonstrate:

✅ Core Java Programming

✅ Object-Oriented Programming (OOP)

✅ Collections Framework

✅ File Handling & Data Persistence

✅ Exception Handling

✅ Business Logic Development

✅ Software Design Principles

✅ Real-World Application Development

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📖 Overview

This repository contains six complete Java console applications developed as part of the SaiKet Systems Java Internship Program. Each task progressively builds on the previous, taking learners from basic Java syntax all the way through full object-oriented design with inheritance, polymorphism, and custom exceptions.

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📁 Full Project Structure

SaiketSystems/
│
├── README.md                          ← This file (master overview)
│
├── Task1_Calculator/
│   ├── Calculator.java
│   └── README.md
│
├── Task2_TempConverter/
│   ├── TemperatureConverter.java
│   └── README.md
│
├── Task3_TodoList/
│   ├── TodoListApp.java
│   └── README.md
│
├── Task4_NumberGuessing/
│   ├── NumberGuessingGame.java
│   └── README.md
│
├── Task5_TextAnalyzer/
│   ├── TextFileAnalyzer.java
│   ├── sample.txt                ← Auto-generated on first run
│   └── README.md
│
└── Task6_BankingSystem/
    ├── BankingSystem.java
    └── README.md

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🗺️ Task Overview

#	Task	File	Difficulty	Key Concept
1	Calculator Application	Calculator.java	⭐ Beginner	Methods, Exception Handling
2	Temperature Converter	TemperatureConverter.java	⭐ Beginner	Methods, Math Operations
3	To-Do List Application	TodoListApp.java	⭐⭐ Intermediate	OOP, ArrayList, Enums
4	Number Guessing Game	NumberGuessingGame.java	⭐⭐ Intermediate	Random, Loops, Logic
5	Text File Analyzer	TextFileAnalyzer.java	⭐⭐⭐ Advanced	File I/O, String Manipulation
6	Basic Banking System	BankingSystem.java	⭐⭐⭐ Advanced	Inheritance, Polymorphism

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🛠️ Skills Progression Map

TASK 1 ──► TASK 2 ──► TASK 3 ──────────► TASK 4 ──► TASK 5 ──► TASK 6
  │           │           │                  │           │           │
Methods    Math Ops    Classes &          Random &    File I/O    Inheritance
Exceptions  Formulas   ArrayList          Loops       Strings     Polymorphism
User Input  Validation  Enums             Statistics  HashMap     Custom Exceptions
Switch-Case Multi-scale CRUD ops          Difficulty  BufferedIO  Abstract Classes

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⚡ Quick Start — Compile & Run All

Prerequisites

• Java JDK 8 or higher
• Verify: java -version and javac -version

One-liner compile script (Linux/macOS)

# From the SaiketSystems root folder:
for dir in Task*/; do
  echo "=== Compiling $dir ==="
  javac "$dir"*.java -d "$dir"
done
echo "All tasks compiled!"

Windows (Command Prompt)

for /d %d in (Task*) do (
  echo === Compiling %d ===
  javac %d\*.java -d %d
)

Run individual tasks

# Task 1
cd Task1_Calculator && javac Calculator.java && java Calculator

# Task 2
cd Task2_TempConverter && javac TemperatureConverter.java && java TemperatureConverter

# Task 3
cd Task3_TodoList && javac TodoListApp.java && java TodoListApp

# Task 4
cd Task4_NumberGuessing && javac NumberGuessingGame.java && java NumberGuessingGame

# Task 5
cd Task5_TextAnalyzer && javac TextFileAnalyzer.java && java TextFileAnalyzer

# Task 6
cd Task6_BankingSystem && javac BankingSystem.java && java BankingSystem

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📋 Detailed Task Descriptions

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Task 1 — Calculator Application

Goal: Build an arithmetic calculator with a user-friendly menu.

Features:

• Six operations: Addition, Subtraction, Multiplication, Division, Modulus, Power
• Division-by-zero and modulus-by-zero exception handling
• Non-numeric input recovery (re-prompts without crashing)
• Continuous operation until user exits

Sample Interaction:

Enter choice: 4
Enter first number : 22
Enter second number: 0
[MATH ERROR] Division by zero is not allowed!

Enter choice: 6
Enter first number : 2
Enter second number: 8
Result: 2.00 ^ 8.00 = 256.000000

Core Skills: static methods, switch-case, try-catch, Scanner

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Task 2 — Temperature Converter

Goal: Convert between Celsius, Fahrenheit, and Kelvin.

Features:

• Any-to-any conversion via Celsius pivot
• Absolute zero boundary validation for all scales
• Shows conversion result AND all three scale equivalents
• Continuous conversion loop

Conversion Formulas Used:

°C → °F : (C × 9/5) + 32
°F → °C : (F − 32) × 5/9
°C →  K : C + 273.15
 K → °C : K − 273.15

Core Skills: Mathematical operations, method decomposition, input validation

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Task 3 — To-Do List Application

Goal: Build a full task manager with priorities, status tracking, and filtering.

Features:

• Add tasks with title, description, and priority (LOW/MEDIUM/HIGH)
• View all tasks with visual priority icons: [!!!] [ ! ] [ ]
• Mark tasks as COMPLETE
• Delete with confirmation prompt
• Filter by status or priority
• View detailed task info
• Live summary header (total / pending / completed)

Class Design:

Task (model) → TaskManager (service) → TodoListApp (UI)

Core Skills: OOP classes & objects, ArrayList, enums, encapsulation

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Task 4 — Number Guessing Game

Goal: Guess a randomly generated number with feedback and difficulty levels.

Features:

• 4 difficulty levels (Easy / Normal / Hard / Expert) with different ranges
• Hot/Cold proximity hints (Very Hot / Warm / Cool / Very Cold)
• Directional arrow hints (Too High / Too Low)
• Visual progress bar: [●●●○○○○] 3/7 used
• Warnings at 2 remaining and last attempt
• Cross-round session statistics (win rate, best round, avg guesses)

Core Skills: java.util.Random, while loops, conditionals, static fields

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Task 5 — Text File Analyzer

Goal: Analyze any .txt file for comprehensive statistics.

Features:

• Counts: lines, words, sentences, paragraphs
• Counts: characters with and without spaces
• Top-10 most frequent word ranking
• Longest line detection
• Reading level estimate (Elementary → Academic)
• Case-insensitive keyword search with line numbers and occurrence counts
• Built-in sample file creator for instant demo

Core Skills: BufferedReader, FileReader, FileWriter, HashMap, regex

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Task 6 — Basic Banking System

Goal: Simulate a multi-account banking system with full OOP.

Features:

• Open Savings (4% annual interest, ₹500 min balance) or Current accounts (₹10K overdraft)
• Deposit, Withdraw, Transfer between accounts
• Check balance (with withdrawable balance for savings)
• Full timestamped transaction history per account
• List all accounts with totals
• Apply monthly interest to all savings accounts
• 3 pre-seeded demo accounts on launch

Inheritance Hierarchy:

BankAccount (abstract)
├── SavingsAccount  → 4% interest, minimum balance rule
└── CurrentAccount  → overdraft facility, no interest

Custom Exceptions:

• InsufficientFundsException (with amount vs available balance detail)
• AccountNotFoundException

Core Skills: Abstract classes, inheritance, polymorphism, custom exceptions, LocalDateTime

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📊 Skills Matrix

Java Concept	T1	T2	T3	T4	T5	T6
Static Methods	✅	✅	✅	✅	✅
Exception Handling	✅	✅			✅	✅
Custom Exceptions						✅
Scanner / User Input	✅	✅	✅	✅	✅	✅
Classes & Objects			✅		✅	✅
Inheritance						✅
Abstract Classes						✅
Polymorphism						✅
Enums			✅		✅	✅
ArrayList			✅		✅	✅
HashMap					✅
Random				✅
File I/O					✅
String Manipulation		✅			✅
Math Operations	✅	✅
Java Time API						✅
Switch-Case	✅	✅	✅		✅	✅
Loops (while/for)	✅	✅	✅	✅	✅	✅

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🧪 Testing Each Task

Task 1 — Calculator

Test	Input	Expected Output
Addition	1, 25, 17	42.000000
Division by zero	4, 10, 0	[MATH ERROR] Division by zero is not allowed!
Power	6, 2, 10	1024.000000
Invalid input	abc	[ERROR] Please enter a valid menu number.

Task 2 — Temperature Converter

Test	Input	Expected
Boiling point	1 (°C), 100	212.0000 °F
Absolute zero	1 (°C), -274	Validation error
Body temp	2 (°F), 98.6 → K	310.1500 K

Task 3 — To-Do List

Action	Result
Add task with empty title	[ERROR] Title cannot be empty.
Mark already-complete task	[INFO] Task already completed.
Delete → n at confirm	Cancelled.

Task 4 — Number Guessing

Scenario	Behaviour
Out-of-range guess	Re-prompts with range reminder
Non-numeric input	[ERROR] Enter a whole number.
2 attempts left	Warning displayed
Correct guess	Congratulation + stats update

Task 5 — Text File Analyzer

Input	Expected
Non-existent file	[ERROR] File not found: ...
Option 3 (sample)	Creates + analyzes sample_text.txt
Search "java"	All line numbers and counts

Task 6 — Banking System

Action	Result
Withdraw > (balance − min) from Savings	InsufficientFundsException
Find non-existent account	AccountNotFoundException
Current account overdraft	Allowed up to ₹10,000
Monthly interest	All savings accounts updated

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👨‍💻 Author & Organization

Field	Info
Organization	SaiKet Systems
Program	Java Training Program
Language	Java 8+
Paradigm	Procedural → Object-Oriented
IDE Recommended	IntelliJ IDEA / VS Code / Eclipse

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📚 Learning Path Recommendation

Week 1  ──► Tasks 1 & 2  (Syntax, methods, math, input)
Week 2  ──► Tasks 3 & 4  (OOP basics, collections, game logic)
Week 3  ──► Tasks 5 & 6  (File I/O, full OOP, inheritance)

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🚀 Extension Challenges

Once comfortable with all 6 tasks, try these upgrades:

1. Task 1+: Add scientific calculator functions (sin, cos, log, sqrt)
2. Task 3+: Persist tasks to a file between sessions (File I/O)
3. Task 4+: Add a leaderboard stored in a file (top 5 scores)
4. Task 5+: Generate an HTML report of the analysis
5. Task 6+: Add PIN authentication and account locking after 3 wrong attempts
6. Combined: Build a CLI that integrates tasks 3 & 6 — a personal finance tracker

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🏆 Internship Highlights

✔ Successfully completed all assigned Java Development tasks.

✔ Built multiple real-world applications using Java.

✔ Applied software engineering best practices.

✔ Demonstrated strong understanding of Core Java and OOP.

✔ Developed practical solutions for automation and data management.

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🤝 Connect With Me

👨‍💻 Amit Kumar Maity

📧 Email: your-email@example.com

💼 LinkedIn: https://linkedin.com/in/your-profile

🌐 GitHub: https://github.com/your-github-username

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Thank You For Visiting 🚀

"Code is not just instructions for machines — it's a craft that reflects your thinking." — SaiKet Systems Java Internship Program