Project: Library Manager

Lab Java Advanced 30 points

Build a small library system. Use a Book class (title, available yes/no) and a HashMap<String, Book>. Read n commands:

add <title> – add a book (print Added <title>, or Already have <title>)
borrow <title> – print Borrowed <title>, <title> is out, or No such book
return <title> – print Returned <title> (if it was out), otherwise Not borrowed (also when the book doesn't exist)

At the end print Available: followed by the available titles in alphabetical order, separated by commas and spaces (or none).

Input

First n, then n commands. Titles are single words.

Output

One line per command, then the Available line.

Example

Input

7
add Dune
add Emma
borrow Dune
borrow Dune
return Emma
add Dune
borrow Ulysses

Output

Added Dune
Added Emma
Borrowed Dune
Dune is out
Not borrowed
Already have Dune
No such book
Available: Emma

Sample input available Sample output available

Editor

Java

Hints

books.get(title) returns null when the book isn't in the map.

A TreeSet sorts the available titles for you.

String.join(", ", set) joins them.

Solution explanation

The map finds a book by title instantly, and each Book object remembers whether it's out.

Show solution

import java.util.HashMap;
import java.util.Scanner;
import java.util.TreeSet;

class Book {
    String title;
    boolean available = true;

    Book(String title) {
        this.title = title;
    }
}

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        HashMap<String, Book> books = new HashMap<>();
        for (int i = 0; i < n; i++) {
            String cmd = sc.next();
            String title = sc.next();
            Book b = books.get(title);
            if (cmd.equals("add")) {
                if (b != null) {
                    System.out.println("Already have " + title);
                } else {
                    books.put(title, new Book(title));
                    System.out.println("Added " + title);
                }
            } else if (cmd.equals("borrow")) {
                if (b == null) {
                    System.out.println("No such book");
                } else if (!b.available) {
                    System.out.println(title + " is out");
                } else {
                    b.available = false;
                    System.out.println("Borrowed " + title);
                }
            } else {
                if (b == null || b.available) {
                    System.out.println("Not borrowed");
                } else {
                    b.available = true;
                    System.out.println("Returned " + title);
                }
            }
        }
        TreeSet<String> free = new TreeSet<>();
        for (Book b : books.values()) {
            if (b.available) free.add(b.title);
        }
        System.out.println("Available: " + (free.isEmpty() ? "none" : String.join(", ", free)));
    }
}

Output

Answer