Admin Interface

Part of the Object Oriented Programming section of Coddy's Java journey — lesson 81 of 87.

Challenge

Easy

Let's expand your Library Management System with an Admin Interface! A real library needs administrative capabilities—adding new books to the collection, removing outdated ones, and registering new members. You'll create an interface that defines these administrative operations and implement them in a dedicated admin class.

You'll continue building on your existing code across five files:

Book.java: Keep your Book class with all existing functionality—isbn, title, author, isAvailable, borrowedBy, getDetails(), and the appropriate getters/setters.
User.java: Keep your User class unchanged with id, name, the borrowedBooks ArrayList, borrowBook(), returnBook(), getBorrowedCount(), and toString().
Library.java: Keep your Library class with all existing methods. Add a new method removeBook(String isbn) that finds and removes a book from the collection by its ISBN. The method should return true if the book was found and removed, false otherwise. A book can only be removed if it's currently available (not borrowed).
LibraryAdmin.java: Create an interface called LibraryAdmin that defines the contract for administrative operations. Your interface should declare three methods:
- addBook(String isbn, String title, String author) - returns a boolean indicating success
- removeBook(String isbn) - returns a boolean indicating success
- registerUser(String id, String name) - returns a boolean indicating success
Then create a class called AdminService that implements this interface. The AdminService should hold a reference to a Library (passed through its constructor) and implement all three methods by delegating to the Library while adding appropriate feedback. When adding a book, create a new Book and add it to the library. When registering a user, create a new User and register them.
Main.java: Demonstrate your admin system! You'll receive a series of admin commands as a single comma-separated string. Each command follows one of these formats:
- ADD_BOOK:isbn:title:author
- REMOVE_BOOK:isbn
- REGISTER_USER:id:name
- BORROW:userId:isbn
Create a Library and an AdminService. Process each command and print the result:
- For ADD_BOOK: print Added: [title] on success
- For REMOVE_BOOK: print Removed: [isbn] on success, or Cannot remove: [isbn] if the book doesn't exist or is borrowed
- For REGISTER_USER: print Registered: [name]
- For BORROW: use the existing library borrow functionality
After processing all commands, print Library status: followed by each book's details and availability status in the format [details] - [Available/Borrowed].

You will receive one input: a comma-separated string of commands.

For example, with input REGISTER_USER:U001:Alice,ADD_BOOK:ISBN-001:Clean Code:Robert Martin,ADD_BOOK:ISBN-002:Design Patterns:Gang of Four,BORROW:U001:ISBN-001,REMOVE_BOOK:ISBN-001,REMOVE_BOOK:ISBN-002, your output would be:

Registered: Alice
Added: Clean Code
Added: Design Patterns
Alice borrowed Clean Code
Cannot remove: ISBN-001
Removed: ISBN-002
Library status:
[ISBN-001] Clean Code by Robert Martin - Borrowed

Notice how the admin interface provides a clean contract for administrative operations, while the AdminService implementation handles the actual logic. The system correctly prevents removing a borrowed book while allowing removal of available ones. This separation of interface and implementation is a key OOP principle that makes your code more maintainable and testable!

Try it yourself

import java.util.Scanner;
import java.util.ArrayList;

class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        // Read the comma-separated commands
        String input = scanner.nextLine();
        String[] commands = input.split(",");
        
        // Create Library and AdminService
        Library library = new Library();
        AdminService adminService = new AdminService(library);
        
        // Process each command
        for (String command : commands) {
            String[] parts = command.split(":");
            String operation = parts[0];
            
            if (operation.equals("ADD_BOOK")) {
                String isbn = parts[1];
                String title = parts[2];
                String author = parts[3];
                if (adminService.addBook(isbn, title, author)) {
                    System.out.println("Added: " + title);
                }
            } else if (operation.equals("REMOVE_BOOK")) {
                String isbn = parts[1];
                if (adminService.removeBook(isbn)) {
                    System.out.println("Removed: " + isbn);
                } else {
                    System.out.println("Cannot remove: " + isbn);
                }
            } else if (operation.equals("REGISTER_USER")) {
                String id = parts[1];
                String name = parts[2];
                if (adminService.registerUser(id, name)) {
                    System.out.println("Registered: " + name);
                }
            } else if (operation.equals("BORROW")) {
                String userId = parts[1];
                String isbn = parts[2];
                library.borrowBook(userId, isbn);
            }
        }
        
        // Print library status
        System.out.println("Library status:");
        ArrayList<Book> allBooks = library.getAllBooks();
        for (Book book : allBooks) {
            String status = book.isAvailable() ? "Available" : "Borrowed";
            System.out.println(book.getDetails() + " - " + status);
        }
    }
}