The ArrayList Notebook

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You created a nice Note class, but now you need a class to store different Notes. In this node, we'll create a simple Class called Notebook which will contain methods for adding, retrieving and listing notes. What structure should be used in Notebook to keep track of its Notes? We've learned about Arrays, so we'll start with a simple Class that uses an array to store Notes:

public class ArrayNotebook
    private Note[] notes;

    /** Constructor for objects of class Notebook */
    public ArrayNotebook()
        notes = new Note[10];

This code declares an array variable for holding Note objects. The constructor initializes an empty Note array with 10 cells.

Limitations of Array
You're now ready to create a method to add Notes to notes, but you right away face the limitation of the simple array - there's no easy way to just add items to an array. You would need to create an index variable just to keep track of where to add the Notes. And what happens when you need to add more than 10 notes when the array is only 10 cells large? Things would get very messy.

Notebook with addNote method

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  • Hi. There is diference between code here in article and code in BlueJ project. What is the right code ?

    private ArrayList notes;

    public Notebook()
  • The answer is in next node. Sory for question.

  • i cant figure it out at all, can anyone help me and just give the right awnsers?

  • I must be missing something obvious.... why do neither of these work:

    fruit.add(String orange);

  • Strings need quotes.

  • Wow... so apparently I don't know what I'm doing here:

    private ArrayList fruit = new ArrayList();

    doesn't work. I understand that would only work INSIDE a class.

    Maybe I just answered my own question.
    Please confirm, why can't I call it private?

  • That's correct. When you're inside a method, every variable you declare can only be accessed inside the method, so you don't use the private modifier.

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