15 Java Projects for All Levels: Build Your Skills and Portfolio in 2025

Beginner Java Projects (5 Projects)

As a beginner, your goal is not to build something huge. You want Java projects that help you practice syntax, conditionals, loops, methods, basic classes and maybe a little file I/O. These Java projects prepare you for the next stage where you begin to learn Java backend development through APIs, databases, and real world project structures.

These first five projects are simple enough to complete in a few days, but rich enough that you can keep improving them over time.

1. Calculator Application

Project details

• You build a simple calculator that works in the console.
• It takes two numbers and an operator from the user.
• It supports addition, subtraction, multiplication, and division.
• You can later upgrade it into a graphical version with buttons and a display.

Key features

• Read numbers and operators from the user.
• Check if the input is valid.
• Do basic arithmetic.
• Handle division by zero.
• Add separate methods for each operation.

Learning outcome

• You learn how to take input, validate it, and perform basic calculations while handling simple errors.

Key Tools and Libraries

• Java Scanner for input
• JavaFX if you build a graphical version later

A simple console version can look like this:

import Java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("First number: ");
        double a = scanner.nextDouble();

        System.out.print("Operator (+, -, *, /): ");
        char op = scanner.next().charAt(0);

        System.out.print("Second number: ");
        double b = scanner.nextDouble();

        double result = switch (op) {
            case '+' -> a + b;
            case '-' -> a - b;
            case '*' -> a * b;
            case '/' -> b != 0 ? a / b : Double.NaN;
            default -> Double.NaN;
        };

        System.out.println("Result: " + result);
    }
}

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2. Number Guessing Game

Project details

• Build a small game where the program picks a random number and the player tries to guess it.
• Give hints such as too high or too low after each guess.
• Start with a fixed range and simple logic, then add difficulty levels or attempt limits.
• Improve it with scoring, high score saving, or a small menu.

Key features

• Generate random numbers
• Read user guesses
• Validate input
• Compare guesses to the target number
• Give hints for each attempt
• Track the number of tries
• Apply difficulty levels
• Save and load high scores
• Show a simple menu

Learning outcome

• You learn how to use loops, conditions, and random numbers in one small game.

Key Tools and Libraries

• Scanner for input
• Random for number generation
• Basic file I O for saving high scores

A simple console version can look like this:

import Java.util.Random;
import Java.util.Scanner;

public class NumberGuessingGame {
    public static void main(String[] args) {
        Random random = new Random();
        int numberToGuess = random.nextInt(100) + 1;
        Scanner scanner = new Scanner(System.in);
        int guess = 0;
        int attempts = 0;

        System.out.println("Guess a number between 1 and 100:");

        while (guess != numberToGuess) {
            System.out.print("Your guess: ");
            if(scanner.hasNextInt()){
                guess = scanner.nextInt();
                attempts++;
                if (guess < numberToGuess) {
                    System.out.println("Too low!");
                } else if (guess > numberToGuess) {
                    System.out.println("Too high!");
                } else {
                    System.out.println("Correct! You guessed it in " + attempts + " tries.");
                }
            } else {
                System.out.println("Please enter a valid number.");
                scanner.next(); // clear invalid input
            }
        }
    }
}

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3. Temperature Converter

Project details

• Create a program where the user selects a conversion type (Celsius to Fahrenheit, Fahrenheit to Kelvin, etc.)
• Enter a value and get the converted result
• Start with a console-based menu, later add a GUI using JavaFX or Swing
• Optionally, add more units, remember past conversions, or validate inputs

Key features

• Read and validate user input
• Convert temperatures using formulas
• Display results clearly
• Use a menu to select conversion type
• Add optional history tracking

Learning outcome

• Practice methods, input validation, and basic math formulas.

Key Tools and Libraries

• Scanner for input
• Methods for modular code
• Basic console output

A simple console version can look like this:

import Java.util.Scanner;

public class TemperatureConverter {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("Choose conversion type:");
        System.out.println("1: Celsius to Fahrenheit");
        System.out.println("2: Fahrenheit to Celsius");
        int choice = scanner.nextInt();

        System.out.print("Enter the temperature: ");
        double temp = scanner.nextDouble();
        double converted = 0;

        switch (choice) {
            case 1 -> converted = (temp * 9/5) + 32;
            case 2 -> converted = (temp - 32) * 5/9;
            default -> System.out.println("Invalid choice");
        }

        System.out.println("Converted temperature: " + converted);
    }
}

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4. To‑Do List Application

Project details

• Create an application to add, list, mark as complete, and remove tasks
• Use an ArrayList or List to store tasks
• Optionally, save tasks to a file and load them on startup
• Later, you can add a GUI with JavaFX, due dates, or categories

Key features

• Add, update, and delete tasks
• Mark tasks as complete
• Store tasks in memory or a file
• Optional GUI interface

Learning outcome

• Learn collections, CRUD operations, and basic file I/O.

Key Tools and Libraries

• ArrayList or List for task storage
• Scanner for input
• FileReader/FileWriter for file storage
• Simple methods for task operations

A simple console version can look like this:

import Java.util.ArrayList;
import Java.util.Scanner;

public class TodoList {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        ArrayList<String> tasks = new ArrayList<>();
        boolean running = true;

        while (running) {
            System.out.println("\n1. Add Task\n2. List Tasks\n3. Remove Task\n4. Exit");
            System.out.print("Choose an option: ");
            int choice = scanner.nextInt();
            scanner.nextLine(); // Consume newline

            switch (choice) {
                case 1 -> {
                    System.out.print("Enter task: ");
                    tasks.add(scanner.nextLine());
                }
                case 2 -> {
                    System.out.println("Tasks:");
                    for (int i = 0; i < tasks.size(); i++) {
                        System.out.println((i + 1) + ". " + tasks.get(i));
                    }
                }
                case 3 -> {
                    System.out.print("Enter task number to remove: ");
                    int taskNum = scanner.nextInt();
                    if (taskNum > 0 && taskNum <= tasks.size()) {
                        tasks.remove(taskNum - 1);
                    } else {
                        System.out.println("Invalid task number.");
                    }
                }
                case 4 -> running = false;
                default -> System.out.println("Invalid choice.");
            }
        }
    }
}

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5. Simple Bank Account System

Project details

• Create an Account class with fields: account number, owner name, balance
• Implement methods for deposit, withdrawal, and balance checking
• Optionally, add transaction history and file storage
• Later, expand to multiple account types, interest calculation, or login system

Key features

• Deposit and withdraw money
• Check current balance
• Maintain transaction history (optional)
• Input validation to prevent negative balances

Learning outcome

• Learn classes, objects, encapsulation, and safe method design

Key Tools and Libraries

• Scanner for user input
• ArrayList for transaction history
• FileReader/FileWriter for saving transactions
• Methods for operations and validations

A simple console version can look like this:

import Java.util.Scanner;

class Account {
    private String owner;
    private int accountNumber;
    private double balance;

    public Account(String owner, int accountNumber, double balance) {
        this.owner = owner;
        this.accountNumber = accountNumber;
        this.balance = balance;
    }

    public void deposit(double amount) {
        if (amount > 0) balance += amount;
        else System.out.println("Invalid amount.");
    }

    public void withdraw(double amount) {
        if (amount > 0 && amount <= balance) balance -= amount;
        else System.out.println("Insufficient balance or invalid amount.");
    }

    public void checkBalance() {
        System.out.println("Balance: $" + balance);
    }
}

public class BankSystem {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Account account = new Account("John Doe", 12345, 500);

        boolean running = true;
        while (running) {
            System.out.println("\n1. Deposit\n2. Withdraw\n3. Check Balance\n4. Exit");
            System.out.print("Choose an option: ");
            int choice = scanner.nextInt();

            switch (choice) {
                case 1 -> {
                    System.out.print("Enter amount to deposit: ");
                    account.deposit(scanner.nextDouble());
                }
                case 2 -> {
                    System.out.print("Enter amount to withdraw: ");
                    account.withdraw(scanner.nextDouble());
                }
                case 3 -> account.checkBalance();
                case 4 -> running = false;
                default -> System.out.println("Invalid choice.");
            }
        }
    }
}

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Intermediate Java Projects (5 Projects)

Once you’ve got a good handle on classes, methods, loops, and collections, you’re ready to take on intermediate Java projects. These projects often involve working with databases, creating graphical interfaces, and handling networking. They usually take a bit longer, typically one to three weeks, but they also introduce concepts you would explore in a Java backend course and give you a much clearer sense of how real-world business applications are built.

6. Library Management System

Project details

• Model books, members, and borrowing operations
• Users can register, search for books, borrow and return items
• Administrators can manage inventory
• Start with a console-based menu; optionally build a JavaFX interface

Key features

• Add, update, and remove books and members
• Borrow and return books
• Search for books by title or author
• Track which member has borrowed which book

Learning outcome

• Learn database connectivity, relational design, and CRUD operations

Key Tools and Libraries

• JDBC for database connection
• MySQL or PostgreSQL for relational database
• Scanner for input
• Apache Maven for dependency management

A simple console version can look like this:

import Java.sql.*;
import Java.util.Scanner;

public class LibrarySystem {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/library";
        String user = "root";
        String password = "password";

        try (Connection conn = DriverManager.getConnection(url, user, password);
             Scanner scanner = new Scanner(System.in)) {

            boolean running = true;
            while (running) {
                System.out.println("\n1. Add Book\n2. Search Book\n3. Borrow Book\n4. Return Book\n5. Exit");
                System.out.print("Choose an option: ");
                int choice = scanner.nextInt();
                scanner.nextLine(); // Consume newline

                switch (choice) {
                    case 1 -> {
                        System.out.print("Book Title: ");
                        String title = scanner.nextLine();
                        System.out.print("Author: ");
                        String author = scanner.nextLine();
                        String sql = "INSERT INTO books (title, author, available) VALUES (?, ?, true)";
                        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
                            stmt.setString(1, title);
                            stmt.setString(2, author);
                            stmt.executeUpdate();
                            System.out.println("Book added successfully.");
                        }
                    }
                    case 2 -> {
                        System.out.print("Enter title to search: ");
                        String search = scanner.nextLine();
                        String sql = "SELECT * FROM books WHERE title LIKE ?";
                        try (PreparedStatement stmt = conn.prepareStatement(sql)) {
                            stmt.setString(1, "%" + search + "%");
                            ResultSet rs = stmt.executeQuery();
                            while (rs.next()) {
                                System.out.println(rs.getInt("id") + ": " + rs.getString("title") + " by " + rs.getString("author"));
                            }
                        }
                    }
                    case 3 -> System.out.println("Borrow book logic here...");
                    case 4 -> System.out.println("Return book logic here...");
                    case 5 -> running = false;
                    default -> System.out.println("Invalid choice.");
                }
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

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7. Online Quiz Application

Project details

• Users can register, choose a quiz category, answer questions, and see their score
• Admin interface to create and manage questions
• Start with a console or basic web interface; optionally use JSP/Servlets or Spring Boot

Key features

• User registration and login
• Display quiz questions and collect answers
• Calculate and display user scores
• Admin panel to add, update, or delete questions

Learning outcome

• Learn client-server architecture, web development basics, and database integration

Key Tools and Libraries

• Java Servlets and JSP or Spring Boot
• MySQL for database
• JDBC for database connectivity
• HTML/CSS for frontend templates

A simple console version can look like this:

import Java.util.*;

public class QuizApp {
    static class Question {
        String question;
        String answer;

        Question(String question, String answer) {
            this.question = question;
            this.answer = answer;
        }
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        List<Question> questions = new ArrayList<>();
        questions.add(new Question("What is Java?", "Programming Language"));
        questions.add(new Question("Capital of France?", "Paris"));

        int score = 0;
        for (Question q : questions) {
            System.out.println(q.question);
            System.out.print("Your answer: ");
            String userAnswer = scanner.nextLine();
            if (userAnswer.equalsIgnoreCase(q.answer)) {
                System.out.println("Correct!");
                score++;
            } else {
                System.out.println("Wrong! Correct answer: " + q.answer);
            }
        }
        System.out.println("Quiz finished! Your score: " + score + "/" + questions.size());
    }
}

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8. Chat Application

Project details

• Create a server component that listens for client connections
• Build a client application that connects to the server
• Relay messages from one client to all other connected clients
• Optionally, create a GUI with JavaFX or Swing

Key features

• Multiple client connections
• Real-time message broadcasting
• Thread management for concurrency
• Optional private messaging or chat rooms

Learning outcome

• Learn networking, multithreading, and basic client-server architecture

Key Tools and Libraries

• Java Sockets for networking
• Input and Output Streams for data transfer
• Threads for concurrency
• JavaFX or Swing for GUI

A simple console version can look like this:

import Java.io.*;
import Java.net.*;
import Java.util.*;

public class Server {
    private static Set<PrintWriter> clientWriters = new HashSet<>();

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(12345);
        System.out.println("Server started on port 12345...");

        while (true) {
            Socket client = serverSocket.accept();
            new Thread(new ClientHandler(client)).start();
        }
    }

    static class ClientHandler implements Runnable {
        private Socket socket;
        private PrintWriter out;

        ClientHandler(Socket socket) {
            this.socket = socket;
        }

        public void run() {
            try (BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()))) {
                out = new PrintWriter(socket.getOutputStream(), true);
                clientWriters.add(out);

                String message;
                while ((message = in.readLine()) != null) {
                    for (PrintWriter writer : clientWriters) {
                        writer.println(message);
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

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9. Inventory Management System

Project details

• Manage products, suppliers, and stock transactions
• Add, update, and delete product information
• Track stock quantities and sales/restocks
• Generate basic inventory reports
• Optional GUI with JavaFX or Swing

Key features

• Product management (CRUD operations)
• Stock level tracking
• Sales and restock logging
• Minimum stock alerts
• Simple reporting

Learning outcome

• Learn database integration, SQL queries, and business logic implementation

Key Tools and Libraries

• JDBC for database connectivity
• SQL for queries and data management
• JavaFX or Swing for GUI
• Collections (ArrayList, HashMap) for in-memory data handling

A simple console version can look like this:

public class Product {
    private String name;
    private int quantity;
    private double price;

    public Product(String name, int quantity, double price) {
        this.name = name;
        this.quantity = quantity;
        this.price = price;
    }

    public String getName() { return name; }
    public int getQuantity() { return quantity; }
    public double getPrice() { return price; }

    public void setQuantity(int quantity) { this.quantity = quantity; }
    public void setPrice(double price) { this.price = price; }
}

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10. Student Management System

Project details

• Manage students, courses, and enrollments
• Track grades, attendance, and student progress
• Role-based access for teachers and administrators
• Generate reports and summaries
• Multi-module architecture with separate logic, database, and UI

Key features

• Student and course CRUD operations
• Enrollment management
• Grade and attendance tracking
• Role-based access control
• Reporting of student performance

Learning outcome

• Learn multi-module project structure
• Practice database integration and SQL queries
• Implement role-based access and data validation
• Gain experience designing scalable educational software

Key Tools and Libraries

• JDBC for database connectivity
• SQL for managing students, courses, and enrollments
• JavaFX or Swing for UI
• Collections (ArrayList, HashMap) for in-memory data handling

A simple console version can look like this:

import Java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student(1, "Alice");
        Student s2 = new Student(2, "Bob");

        Course c1 = new Course("CS101", "Computer Science Basics");
        Course c2 = new Course("MATH101", "Calculus I");

        Enrollment enrollment = new Enrollment();
        Scanner scanner = new Scanner(System.in);

        while (true) {
            System.out.println("1. Enroll Student\n2. List Enrollments\nChoose option:");
            int option = scanner.nextInt();
            scanner.nextLine(); // consume newline

            if (option == 1) {
                System.out.println("Enter student name (Alice/Bob):");
                String name = scanner.nextLine();
                Student selectedStudent = name.equalsIgnoreCase("Alice") ? s1 : s2;

                System.out.println("Enter course code (CS101/MATH101):");
                String code = scanner.nextLine();
                Course selectedCourse = code.equalsIgnoreCase("CS101") ? c1 : c2;

                enrollment.enroll(selectedStudent, selectedCourse);
            } else if (option == 2) {
                enrollment.listEnrollments();
            }
        }
    }
}

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Advanced Java Projects (5 Projects)

When you reach the advanced stage, your Java projects begin to look like real products. You will work with frameworks, security, performance optimization, and sometimes explore machine learning or IoT. 

Advanced projects are more complex and take more time, but they closely reflect the kind of work you might do in a professional setting. You do not need to rush. Once you feel confident with intermediate projects and core Java, you can choose an advanced project and work on it at your own pace.

11. E‑Commerce Platform

Project details

• Manage product catalog, user accounts, and shopping carts
• Place orders and track order history
• Admin panel to manage inventory and prices
• Optionally simulate a payment gateway
• Console-based or full web-based frontend (Spring Boot/React/Angular)

Key features

• Add, view, update, and delete products
• User registration and login
• Shopping cart management
• Place and track orders
• Admin operations on inventory

Learning outcome

• Prepare for advanced frameworks like Spring Boot and Hibernate

Key Tools and Libraries

• Collections (ArrayList, HashMap) for products, users, and carts
• Scanner for console input
• Basic file I/O for storing orders or inventory
• Methods for handling cart and order logic
  

A simple console version can look like this:

import Java.util.*;

class Product {
    String name;
    double price;

    Product(String name, double price) {
        this.name = name;
        this.price = price;
    }
}

class User {
    String username;
    List<Product> cart = new ArrayList<>();

    User(String username) {
        this.username = username;
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Sample products
        List<Product> products = new ArrayList<>();
        products.add(new Product("Laptop", 1200));
        products.add(new Product("Phone", 700));

        // Sample user
        User user = new User("Alice");

        while (true) {
            System.out.println("\n1. View Products\n2. Add to Cart\n3. View Cart\n4. Checkout");
            System.out.print("Choose option: ");
            int option = scanner.nextInt();
            scanner.nextLine(); // consume newline

            if (option == 1) {
                System.out.println("Products available:");
                for (int i = 0; i < products.size(); i++) {
                    System.out.println((i+1) + ". " + products.get(i).name + " - $" + products.get(i).price);
                }
            } else if (option == 2) {
                System.out.print("Enter product number to add to cart: ");
                int p = scanner.nextInt() - 1;
                if (p >= 0 && p < products.size()) {
                    user.cart.add(products.get(p));
                    System.out.println(products.get(p).name + " added to cart.");
                } else {
                    System.out.println("Invalid product number.");
                }
            } else if (option == 3) {
                System.out.println("Cart contents:");
                for (Product p : user.cart) {
                    System.out.println("- " + p.name + " $" + p.price);
                }
            } else if (option == 4) {
                double total = 0;
                for (Product p : user.cart) total += p.price;
                System.out.println("Order placed. Total: $" + total);
                user.cart.clear();
            }
        }
    }
}

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12. Smart Home Automation System

Project details

• Control devices like lights, thermostats, and sensors
• Simulate or integrate with real IoT devices
• Set schedules and automation rules
• Visualize device status in a console or GUI

Key features

• Turn devices on/off
• Adjust settings (temperature, brightness, etc.)
• Respond to sensor data (e.g., temperature triggers heater)
• View current device states

Learning outcome

• Gain experience for future IoT, AI, or ML projects

Key Tools and Libraries

• Collections (HashMap, ArrayList) to store device states
• Scanner for console input
• Methods for device actions and automation rules
• Optional: file I/O for persisting device states

A simple console version can look like this:

import Java.util.*;

class Device {
    String name;
    boolean isOn;

    Device(String name) {
        this.name = name;
        this.isOn = false;
    }

    void turnOn() {
        isOn = true;
        System.out.println(name + " turned ON.");
    }

    void turnOff() {
        isOn = false;
        System.out.println(name + " turned OFF.");
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Simulated devices
        Map<String, Device> devices = new HashMap<>();
        devices.put("Light", new Device("Light"));
        devices.put("Heater", new Device("Heater"));
        devices.put("AC", new Device("AC"));

        while (true) {
            System.out.println("\n1. Toggle Light\n2. Toggle Heater\n3. Toggle AC\n4. Show Status");
            System.out.print("Choose option: ");
            int choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    toggleDevice(devices.get("Light"));
                    break;
                case 2:
                    toggleDevice(devices.get("Heater"));
                    break;
                case 3:
                    toggleDevice(devices.get("AC"));
                    break;
                case 4:
                    showStatus(devices);
                    break;
                default:
                    System.out.println("Invalid choice.");
            }
        }
    }

    static void toggleDevice(Device device) {
        if (device.isOn) device.turnOff();
        else device.turnOn();
    }

    static void showStatus(Map<String, Device> devices) {
        System.out.println("Device Status:");
        for (Device d : devices.values()) {
            System.out.println("- " + d.name + ": " + (d.isOn ? "ON" : "OFF"));
        }
    }
}

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13. Hospital Management System

Project details

• Manage patient records, appointments, billing, and prescriptions
• Handle multiple roles: doctors, nurses, administrators
• Emphasize security, privacy, and role-based access
• Include logging and data validation

Key features

• Add, update, and delete patient records
• Schedule and view appointments
• Generate basic billing information
• Track prescriptions for patients
• Role-based access simulation (admin, doctor, nurse)

Learning outcome

• Gain experience in logging, validation, and modular design

Key Tools and Libraries

• Scanner for input
• Collections (ArrayList, HashMap) to store records
• Methods for CRUD operations and role-based logic
• Optional: file I/O for data persistence
• Optional frameworks for real projects: Spring Boot, Jakarta EE, Log4j

A simple console version can look like this:

import Java.util.*;

class Patient {
    String id;
    String name;
    int age;

    Patient(String id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
}

public class Main {
    static Scanner scanner = new Scanner(System.in);
    static Map<String, Patient> patients = new HashMap<>();

    public static void main(String[] args) {
        while (true) {
            System.out.println("\n1. Add Patient\n2. View Patient\n3. Delete Patient\n4. List All Patients");
            System.out.print("Choose option: ");
            int choice = scanner.nextInt();
            scanner.nextLine(); // consume newline

            switch (choice) {
                case 1: addPatient(); break;
                case 2: viewPatient(); break;
                case 3: deletePatient(); break;
                case 4: listPatients(); break;
                default: System.out.println("Invalid choice.");
            }
        }
    }

    static void addPatient() {
        System.out.print("Enter Patient ID: ");
        String id = scanner.nextLine();
        System.out.print("Enter Name: ");
        String name = scanner.nextLine();
        System.out.print("Enter Age: ");
        int age = scanner.nextInt();
        scanner.nextLine(); // consume newline
        patients.put(id, new Patient(id, name, age));
        System.out.println("Patient added successfully.");
    }

    static void viewPatient() {
        System.out.print("Enter Patient ID: ");
        String id = scanner.nextLine();
        Patient p = patients.get(id);
        if (p != null) {
            System.out.println("Patient ID: " + p.id + ", Name: " + p.name + ", Age: " + p.age);
        } else {
            System.out.println("Patient not found.");
        }
    }

    static void deletePatient() {
        System.out.print("Enter Patient ID: ");
        String id = scanner.nextLine();
        if (patients.remove(id) != null) {
            System.out.println("Patient deleted successfully.");
        } else {
            System.out.println("Patient not found.");
        }
    }

    static void listPatients() {
        if (patients.isEmpty()) {
            System.out.println("No patients found.");
        } else {
            System.out.println("Patient List:");
            for (Patient p : patients.values()) {
                System.out.println("- " + p.id + ": " + p.name + ", Age " + p.age);
            }
        }
    }
}

‍

14. Face Detection & Recognition System

Project details

• Detect faces in images or video frames
• Recognize faces by comparing with a stored dataset
• Practice computer vision and basic machine learning concepts
• Integrate external libraries for image processing and ML

Key features

• Load and preprocess images
• Detect faces using OpenCV
• Recognize faces using a simple dataset
• Display detection and recognition results
• Optional: store recognized faces and statistics

Learning outcome

• Understand Java bindings for OpenCV and ML libraries

Key Tools and Libraries

• OpenCV (Java bindings) for image processing
• Deeplearning4j or Apache Mahout for ML tasks
• Scanner for input in console prototype
• Methods for preprocessing, detection, and recognition logic
• Optional: file I/O for storing face datasets

A simple console version can look like this:

import org.opencv.core.*;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.objdetect.CascadeClassifier;

import Java.util.Scanner;

public class Main {
    static { System.loadLibrary(Core.NATIVE_LIBRARY_NAME); }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter path to image: ");
        String imagePath = scanner.nextLine();

        CascadeClassifier faceDetector = new CascadeClassifier("haarcascade_frontalface_alt.xml");
        Mat image = Imgcodecs.imread(imagePath);

        if (image.empty()) {
            System.out.println("Image not found!");
            return;
        }

        MatOfRect faceDetections = new MatOfRect();
        faceDetector.detectMultiScale(image, faceDetections);

        System.out.println("Detected " + faceDetections.toArray().length + " face(s).");
        for (Rect rect : faceDetections.toArray()) {
            System.out.println("Face at [x=" + rect.x + ", y=" + rect.y + ", width=" + rect.width + ", height=" + rect.height + "]");
        }

        // Optional: integrate ML model for recognition here
        System.out.println("Face recognition can be added using Deeplearning4j or Apache Mahout.");
    }
}

‍

15. Blockchain Implementation

Project details

• Build a simplified blockchain in Java
• Each block contains data and hash of the previous block
• Implement proof-of-work and validation mechanisms
• Explore distributed ledger concepts and data integrity

Key features

• Create blocks with data and hashes
• Chain blocks with previous block hashes
• Validate the integrity of the blockchain
• Simple proof-of-work mechanism
• Optional: simulate peer-to-peer network for block propagation

Learning outcome

• Understand blockchain structure and block linking
• Learn hashing and basic cryptography in Java
• Implement data integrity and chain validation
• Explore distributed system and consensus concepts
• Practice object-oriented design for complex data structures

Key Tools and Libraries

• MessageDigest for SHA-256 hashing
• ArrayList for storing the blockchain
• Scanner for console input
• Methods for block creation, validation, and proof-of-work
• Optional: file I/O for storing blockchain data

A simple console version can look like this:

import Java.security.MessageDigest;
import Java.util.ArrayList;
import Java.util.Scanner;

class Block {
    public String data;
    public String previousHash;
    public String hash;
    public int nonce;

    public Block(String data, String previousHash) {
        this.data = data;
        this.previousHash = previousHash;
        this.nonce = 0;
        this.hash = calculateHash();
    }

    public String calculateHash() {
        try {
            String input = previousHash + data + nonce;
            MessageDigest digest = MessageDigest.getInstance("SHA-256");
            byte[] hashBytes = digest.digest(input.getBytes("UTF-8"));
            StringBuilder hexString = new StringBuilder();
            for (byte b : hashBytes) {
                String hex = Integer.toHexString(0xff & b);
                if (hex.length() == 1) hexString.append('0');
                hexString.append(hex);
            }
            return hexString.toString();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void mineBlock(int difficulty) {
        String target = new String(new char[difficulty]).replace('\0', '0');
        while (!hash.substring(0, difficulty).equals(target)) {
            nonce++;
            hash = calculateHash();
        }
        System.out.println("Block mined: " + hash);
    }
}

public class Main {
    public static ArrayList<Block> blockchain = new ArrayList<>();
    public static int difficulty = 4;

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter data for the first block: ");
        String data = scanner.nextLine();
        Block genesisBlock = new Block(data, "0");
        genesisBlock.mineBlock(difficulty);
        blockchain.add(genesisBlock);

        System.out.print("Enter data for the next block: ");
        data = scanner.nextLine();
        Block block2 = new Block(data, blockchain.get(blockchain.size() - 1).hash);
        block2.mineBlock(difficulty);
        blockchain.add(block2);

        System.out.println("\nBlockchain:");
        for (Block block : blockchain) {
            System.out.println("Data: " + block.data);
            System.out.println("Hash: " + block.hash);
            System.out.println("Previous: " + block.previousHash + "\n");
        }
    }
}

‍

Time to Level Up

Java remains one of the most reliable paths into software development. It is used by Fortune 500 companies, runs on billions of devices, and has a global community of more than 10 million developers. The ecosystem keeps expanding, which makes Java a strong long-term skill for anyone building a tech career.

It is also more approachable than many expect. Most developers say Java is not difficult to learn when you follow a clear plan and practice consistently, especially when pairing hands-on projects with structured study through Java backend courses.

The 15 projects in this guide give you a clear progression from simple console apps to complex systems. Start with a beginner project you can finish quickly, then move to intermediate projects with databases, and finally try advanced projects that match your interests and career goals.

Using a guided platform like Hyperskill can help, providing a structured path, real projects, and feedback. The most important step is to start. Pick a project, open your IDE, and write the first line of code. Each completed project brings you closer to a job-ready portfolio.