Thread: how to take array input from main method and use it in one of the classes

QUESTION
I have to find total number of different books in method getdiffCount().

package module4c;
 
class Book{
	String title;
	String author;
	int count;
 
	public Book(){
 
	}
	public Book(String title,String author,int count){
		this.title=title;
		this.author = author;
		this.count=count;
	}
 
	public void increment(int i){
		i=i+1;
	}
 
	public void decrement(int i){
		if(i>0){
			i=i-1;
		}
	}
 
}
 
class Library{
	Book [] books;
 
	public Library() {
		// TODO Auto-generated constructor stub
	}
	public Library(Book[] books){
		this.books= books;
	}
 
public int getdiffCount(){
	int bs=0;
 
   bs = bs +books.length;
 
		System.out.println(bs);
		return bs;
		}
 
 }
public class TestLibrary {
 
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Library lib = new Library();
      Book book0 = new Book("A","AB",10);
      Book book1 = new Book("B","CD",20);
      Book book2 = new Book("C","EF",30);
      Book book3 = new Book("D","GH",40);
      Book [] books ={book0,book1,book2,book3};
 
 
      int b3 = lib.getdiffCount();

QUESTION
I have to find total number of different books in method getdiffCount().

 
package module4c;
 
class Book{
	String title;
	String author;
	int count;
 
	public Book(){
 
	}
	public Book(String title,String author,int count){
		this.title=title;
		this.author = author;
		this.count=count;
	}
 
	public void increment(int i){
		i=i+1;
	}
 
	public void decrement(int i){
		if(i>0){
			i=i-1;
		}
	}
 
}
 
class Library{
	Book [] books;
 
	public Library() {
		// TODO Auto-generated constructor stub
	}
	public Library(Book[] books){
		this.books= books;
	}
 
public int getdiffCount(){
	int bs=0;
 
   bs = bs +books.length;
 
		System.out.println(bs);
		return bs;
		}
 
 }
public class TestLibrary {
 
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Library lib = new Library();
      Book book0 = new Book("A","AB",10);
      Book book1 = new Book("B","CD",20);
      Book book2 = new Book("C","EF",30);
      Book book3 = new Book("D","GH",40);
      Book [] books ={book0,book1,book2,book3};
 
 
      int b3 = lib.getdiffCount();

Threads merged. Please don't post the same topic multiple times.

Perhaps you could declare 'count' to be a class variable and increment that each time a book is created.

Your increment() and decrement() methods are pointless.

thanks...
i was trying to find out the total no of different books (ie 4 is the answer).so , i thought that if i could find the length of the Book [] books, i would get my answer. Is my approach correct???. if so how would i do it.

If that way of approach is not correct , then please suggest the correct approach.

--- Update ---

i was also wondering if the concept of interface would do some good???

i thought that if i could find the length of the Book [] books, i would get my answer. Is my approach correct???

There are multiple approaches, all of them 'correct'. If books[] has no duplicates, yes, that should work. Will you be certain that books[] has only unique entries? Arrays in Java have an attribute 'length', so myArray.length will give you the number of elements in the array myArray. You can discover these interesting and useful facts yourself by referring to the appropriate API pages.

Also, a class variable 'count' or 'uniqueCount' that is incremented each time a unique book is added to the array should also provide quick access to the needed value.

Why do you ask about an interface? Is your program supposed to include one? Other than a requirement or chance for extra credit, I don't see value in squeezing one in to accomplish what you've described so far.

Doubt
i tried using attribute 'length' but in (books.length) 'books' corresponds to Book[].module 4c but it should correspond to my input Book[] books.
i am giving the code plz help.

package module4c;
 
class Book{
	String title;
	String author;
	int count;
 
	public Book(){
 
	}
	public Book(String title,String author,int count){
		this.title=title;
		this.author = author;
		this.count=count;
	}
class Library{
	Book [] books;
 
	public Library() {
		// TODO Auto-generated constructor stub
	}
	public Library(Book[] books){
		this.books= books;
 
	}
public int getdiffCount(){
	int bs=0;
 
   bs = bs +books.length;
 
		System.out.println(bs);
		return bs;
		}
public class TestLibrary {
 
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Library lib = new Library();
      Book book0 = new Book("A","AB",10);
      Book book1 = new Book("B","CD",20);
      Book book2 = new Book("C","EF",30);
      Book book3 = new Book("D","GH",40);
      Book [] books ={book0,book1,book2,book3};
 
      int b1 = lib.getCount(book1);
      int b2 = lib.getCount("A");
      int b3 = lib.getdiffCount();
      int b4 = lib.addBook(book3);
 
      System.out.println();
	}

--- Update ---

can it be achieved using get or set method???

It's hard to tell what's going on with your code the way you've posted it. For example, the TestLibrary class is a Library nested class. Reorganize your code and indent it properly so that TestLibrary is THE top-level public class and all other classes are appropriately organized. Post your updated code when able.

is it correct now

 
package module4c;
 
class Book{
	String title;
	String author;
	int count;
 
	public Book(){
 
	}
	public Book(String title,String author,int count){
		this.title=title;
		this.author = author;
		this.count=count;
	}
class Library{
	Book [] books;
 
	public Library() {
		// TODO Auto-generated constructor stub
	}
	public Library(Book[] books){
		this.books= books;
 
	}
public int getdiffCount(){
	int bs=0;
 
   bs = bs +books.length;
 
		System.out.println(bs);
		return bs;
		}
}
public class TestLibrary {
 
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Library lib = new Library();
      Book book0 = new Book("A","AB",10);
      Book book1 = new Book("B","CD",20);
      Book book2 = new Book("C","EF",30);
      Book book3 = new Book("D","GH",40);
      Book [] books ={book0,book1,book2,book3};
 
      int b1 = lib.getCount(book1);
      int b2 = lib.getCount("A");
      int b3 = lib.getdiffCount();
      int b4 = lib.addBook(book3);
 
      System.out.println();
	}

No. Now TestLibrary is a Book nested class. I will repost your code indented correctly but still incorrectly organized. See if you can reorganize the code correctly while preserving correct indentation. Post your results.

class Book{
    String title;
    String author;
    int count;
 
    public Book(){
 
    }
    public Book(String title,String author,int count){
        this.title=title;
        this.author = author;
        this.count=count;
    }
    class Library{
        Book [] books;
 
        public Library() {
            // TODO Auto-generated constructor stub
        }
        public Library(Book[] books){
            this.books= books;
 
        }
        public int getdiffCount(){
            int bs=0;
 
            bs = bs +books.length;
 
            System.out.println(bs);
            return bs;
        }
    }
    public class TestLibrary {
 
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            Library lib = new Library();
            Book book0 = new Book("A","AB",10);
            Book book1 = new Book("B","CD",20);
            Book book2 = new Book("C","EF",30);
            Book book3 = new Book("D","GH",40);
            Book [] books ={book0,book1,book2,book3};
 
            int b1 = lib.getCount(book1);
            int b2 = lib.getCount("A");
            int b3 = lib.getdiffCount();
            int b4 = lib.addBook(book3);
 
            System.out.println();
        }
    }
}

What are you using for a source code editor or IDE?

i am using eclipse as IDE

i hope its correct now...

 
class Book{
    String title;
    String author;
    int count;
 
    public Book(){
 
    }
    public Book(String title,String author,int count){
        this.title=title;
        this.author = author;
        this.count=count;
    }
    class Library{
        Book [] books;
 
        public Library() {
            // TODO Auto-generated constructor stub
        }
        public Library(Book[] books){
            this.books= books;
 
        }
        public int getdiffCount(){
            int bs=0;
 
            bs = bs +books.length;
 
            System.out.println(bs);
            return bs;
        }
    }
}
    public class TestLibrary {
 
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            Library lib = new Library();
            Book book0 = new Book("A","AB",10);
            Book book1 = new Book("B","CD",20);
            Book book2 = new Book("C","EF",30);
            Book book3 = new Book("D","GH",40);
            Book [] books ={book0,book1,book2,book3};
 
            int b1 = lib.getCount(book1);
            int b2 = lib.getCount("A");
            int b3 = lib.getdiffCount();
            int b4 = lib.addBook(book3);
 
            System.out.println();
        }
    }
}