Errors when compiling

Question

I am trying to turn my array into an arraylist and I am having trouble modifying this part of my class. I don't have my complete class but this part of it.

   public boolean add(String title, int productID){//true or false statement

        if ( numberOfRecords == list.length() ){  // I get an error here at list.length()
    return false;

}
    else
    { list [numberOfRecords] = new MyArrayList(title, productID);// I get an error
    numberOfRecords++;
    return true;
    }

}

Answer 1

It's impossible to tell from the snippet you've provided. There are too many variables that are unknown. But Paul Tomblin is correct: List doesn't have a length() method, but array has a length attribute. Which one describes your list variable?

Compiler issues should almost NEVER be part of a question here. When the compiler gives you a message, it's likely to give you enough information to figure it out with a little research.

When you post a question asking about compilation issues, it says that you weren't willing to invest enough energy or effort to figure it out for yourself.

This works properly. See how your code compares:

package movie;

/**
 * ShoppingCart
 * User: Michael
 * Date: 10/16/10
 * Time: 8:07 PM
 */
public class ShoppingCart
{
    private Movie[] list;
    private int numberOfRecords;

    public static void main(String[] args)
    {
        ShoppingCart cart = new ShoppingCart(args.length);
        for (int i = 0; i < args.length; ++i)
        {
            boolean success = cart.add(args[i], i);
            System.out.println("Movie '" + args[i] + (success ? "' was " : " was not ") + "added successfully");
        }
        boolean success = cart.add("Gladiator", args.length+1);
        System.out.println("Movie 'Gladiator'" + (success ? " was " : " was not ") + "added successfully");

        System.out.println(cart);
    }

    public ShoppingCart(int numberOfRecords)
    {
        this.numberOfRecords = 0;
        this.list = new Movie[numberOfRecords];
     }

    @Override
    public String toString()
    {
        StringBuilder builder = new StringBuilder();

        String newline = System.getProperty("line.separator");
        for (Movie movie : this.list)
        {
            builder.append(movie).append(newline);
        }

        return builder.toString();
    }

    public boolean add(String title, int productId)
    {
        if (numberOfRecords == list.length)
        {
            return false;
        }
        else
        {
            list[numberOfRecords] = new Movie(productId, title);
            numberOfRecords++;
            return true;
        }


    }
}

class Movie
{
    private int id;
    private String title;

    Movie(int id, String title)
    {
        this.id = id;
        this.title = title;
    }

    public String getTitle()
    {
        return title;
    }

    @Override
    public String toString()
    {
        return "Movie{" +
               "id=" + id +
               ", title='" + title + '\'' +
               '}';
    }
}

Answer 2

to call list [numberOfRecords], list must be an array instance.

Hovewer,

if ( numberOfRecords == list.length() ){  // I get an error here at list.length()
    return false;
}

this section of your code says that list is an java.util.List implementation instance.

You should modify

list [numberOfRecords] = new Movie(title, productID);

this section to:

list.add(new Movie(title, productID));

Answer 3

To use a List in place of an array you'll have to make the following changes:

list.length() to list.size()

list [numberOfRecords] list.add(new Movie(title, productID))

Answer 4

It seems that you are implementing your own ArrayList. So list is the array and numberOfRecords is the number of elements that are present and filled-out in the array.

If that's correct, you should not call your array list, since the name is misleading. A better name would be elements.

And, as others have noted, arrays don't have a method length, it's a field instead. So you should write elements.length instead of elements.length().