Java: Object 阵列内 Object 阵列

Question

I'm building a library program, which has 4 classes:

• Books ==> contains the title of a book
• Genre ==> contains the name of a genre and an object array of books
• Library ==> contains an object array of genres
• App ==> contains the dialog and scanner

You'll be able to create new genre arrays and new book arrays from the app class.

public class App{
  Library library = new Library();

  //the other stuff

  private void run(){
     library.addGenres(insertGenreNameHere);
  }
}


public class Library{
   private Genres[] genres = new Genres[5];    //Obj. Array of genres
   private Int nrOfGenres = 0;                 //number of how many genres there are in an array

    public void addGenres(String genreName){   //adds a new genre to the array
       if (nrOfGenres < genres.length) {
        genres[nrOfGenres] = new Genres(genreName);
        nrOfGenres++;
    }
    else {
        System.out.println("You already have the maximum of " + genres.length + " genres!");
    }
}



public class Genres {

   private String name;
   private Books[] books = new Books[5];        //Obj. Array of books
   private int nrOfBooks = 0;                   //number of how many books there are in an array

   public Genres(String name) {                 //Constructor
       this.name = name;
   }

   //getter & setter for the name of the genre

   public void addBooks(String titel){          //adds new book to the array
      if (nrOfBooks < books.length) {
         books[nrOfBooks] = new Books(titel);
         nrOfBooks++;
    }
    else {
        System.out.println("You already have the maximum of " + books.length + " books!");
    }
}

public void showBooks(){                        //prints the books line by line
    int x = 0;
    while(x < books.length && books[x] != null) {
        System.out.println(books[x].getTitle());
        x++;
    }
  }
}



public class Books(){
   private String title;

   public Books(String title){                  //Constructor
      this.title = title;
   }

   //getter & setter for the title
}

However I yet don't know how I can add a book to its genre or even how I should "contact"(?) a book

If im correct I cant just do Genre genre = new Genre(); or Books books = new Book(); because it has to be in an array (?)

I'd be very glad if one could help me and happy to share more information if needed

Cheers Martin

Answer 1

Are you sure that the number of books and number of genres will be constant? I believe converting books and genres from arrays to ArrayList should help you achieve a smooth run of the program. You do not need to keep a count on number of books and number of genres. Things can be much simpler when you use an ArrayList and its size() method.