How to implement two dimensional object array?

Question

I want to implement a two-dimensional array using user input. I have a Book class. It has two variables: int price and String name. I want to store 5 books information in a two-dimensional array. Book class code is below:

public class Book {
    String name;
    int price;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getPrice() {
        return price;
    }

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

Main Class code:

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int l = 5;
    Book[][] bk = new Book[l][l];
    for (int i = 0; i < l; i++) {
        for (int j = 0; j < l; j++) {
            // here i want to take user input.
            System.out.println("Enter Song: ");
            String sname = in.next();
            System.out.println("Enter price: ");
            int sprice = in.nextInt();
            // in this line i am getting type
            // error int can't convert to string
            song[i][j] = song[sname][price];
        }
    }
}

you cannot use sname which of type String as index of array. if sname is int value in String, use Integer.parseInt — sidgate
– sidgate, Commented Jun 15, 2020 at 14:31
brother, how can I convert a book name to an integer? I want to input a book name and price in a two-dimensional array. so the name should be string and price should be int, double, or float. — Almamun
– Almamun, Commented Jun 15, 2020 at 14:42
This sounds like a place where Java.util.Dictionary Class would be useful. The developer here might consider implementing a key (some unique integer or unique string, perhaps) so that you can collect the data more easily in a Dictionary, which consists of Key-Value pairs. — Su Llewellyn
– Su Llewellyn, Commented Jun 15, 2020 at 21:46

Andrea Felline · Accepted Answer · 2020-06-15 14:56:07Z

1

You never declared the array song, maybe you wanted to write

bk[i][j] = ...

Now you want to create a new "Book" for every sname and sprice that you read, so you have two options:

1) In each iteration create a new empty Book

Book tmp = new Book();

then you set his Name and his Price

tmp.setName(sname);
tmp.setPrice(sprice);

and then you assign the new Book to the current element of bk

bk[i][j] = tmp;

or

2) Add a constructor to the class Book that has Name and Price as parameters

public Book(String n, int p){
    name = n;
    price = p;
}

and use it to instantly create a new Book and assign it to the current element of bk

bk[i][j] = new Book(sname, sprice);

answered Jun 15, 2020 at 14:56

Andrea Felline

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3 Comments

Almamun Over a year ago

thanks for your answer. but what about bk[][] variable types?

Andrea Felline Over a year ago

@Almamun each element in bk is a Book, so it contains a name and a price

Almamun Over a year ago

yes, I got that. but that way it doesn't work. then I define one-dimensional array Book bk[] = new Book[l]; and used only one for loop and then just set the value using the constructor. bk[i]= new Book(name,price);

Community · Accepted Answer · 2021-06-11 06:49:42Z

1

So what you require is Book[String name][int price]. That is not how 2D arrays work.

While declaring:

int l = 5;
Book[][] bk = new Book[l][l];

You are implementing a 2D Book array that can have 25 book records. 1D array of Books is sufficient for your requirements.

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int l = 25;//any size you can have
    Book[] bk = new Book[l];
    for (int i = 0; i < l; i++) {
        System.out.println("Enter Song: ");
        String sname = in.next();
        System.out.println("Enter price: ");
        int sprice = in.nextInt();
        Book book = new Book();
        book.setName(sname);
        book.setprice(sprice);
        bk[i] = book;
    }
}

edited Jun 11, 2021 at 6:49

CommunityBot

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answered Jun 17, 2020 at 13:50

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