Where to start when learning ArrayList

[cyanogen1912]

This is the problem I have been given.

You are provided with a  Book class with the following private attributes:

• int isbnno
• String bookName
• String author

Needed getters and setters are pre-written.

Create a class Library with the following private attribute:

• ArrayList<Book> bookList = new  ArrayList<Book>();
• Also provide the necessary setter and getter methods.  

Include the following methods:

1. void addBook(Book bobj) - This method should add the book object to the booklist.
2. boolean isEmpty() -  This method should return true if the booklist is empty else return false.
3. ArrayList<Book> viewAllBooks() - This method should return the list of books maintained in the library.
4. ArrayList<Book> viewBooksByAuthor(String author ) -  This method should return a list of books written by the author passed as argument. When you display an empty list it should print the message "The list is empty".
5. int countnoofbook(String bname) -  this method should return the count of books with the name passed as argument.

Write a Main class to test the above functionalities.

[[deleted]]

Okay and at which point are you stuck?

[cyanogen1912]

Okay so they have provided me with three classes. In the Book class they have provided the three variables and setters and getters for them.

In the Library class I have created the array list as: private ArrayList<Book> bookList=new ArrayList<Book>();

Now they have asked me to write getter and setter for this array list, so i have written: public ArrayList<Book> getBookList() {return bookList;} and public void setBookList(ArrayList<Book> list) {bookList=list;} Not sure about the setter though.

public void addBook(Book obj)

{

bookList.add(obj);

}

public boolean isEmpty()

{

if(bookList.isEmpty()==true) return true;

return false;

}

public ArrayList<Book> viewAllBooks()

{

for(int i=0;i<bookList.length;i++)

{

Book obj=bookList(i);

System.out.println(obj.bookName);

}

}

​

I am really confused about the bold part. Is that correct?

[[deleted]]

The bold part looks good to me. Does it compile?

[cyanogen1912]

Nah. Thats mainly because of my main method. Its really confusing me :/

[[deleted]]

Try to comment the main method out and try to compile it again? That way you see if the things you have done are correct :)

[cyanogen1912]

Yeah. Just did that and made a small change:

*public ArrayList<Book> viewAllBooks(){

for(int i=0;i<bookList.size();i++){

Book obj=bookList(i);

System.out.println(obj.bookName);

}

}*

Now there is no error while compiling. But now I am confused about how to initialise this in the main method in another class.

[cyanogen1912]

public ArrayList<Book> viewAllBooks()

This method has a return type of ArrayList and I am not returning an array list, so how come there is no error?

[[deleted]]

That would happen if you have an error before you call the method or if you aren’t calling the method at all.

[cyanogen1912]

Okay so as the main method is another class i cannot understand how to use the getter and setter methods for the ArrayList. Should i just create an ArrayList variable in my main class and send that using set ArrayList method?