Array of class objects in android

Question

I have constructed a class to mimic a C# struct:

public class Favourite {
    protected  String favName;
    protected  String favText;
    protected String favDelay;
    protected GeoPoint favPoint;
    protected Uri favUri;
}

I want to create an array of this class:

Favourite[] fav;

When I try to access this array:

fav[s].favName = bufr;

I get a NullPointerException. bufr does contain data. I have tracked it down to accessing the array as the following code:

fav[s].favName = "";

also produces a NullPointerException.

I have searched high and low for some indication as to whether or not what I am doing is allowed but cannot find anything.

I suppose my questions are:

Are you allowed to create an array of a class object? If so, how do you refer to that array?

I know I could do this using five separate arrays of the variables but I feel that putting them into a class gives a better structure and is more elegant (I like elegance).

Have you initialized fav[s] such that favName exists?

BlackVegetable
– BlackVegetable

2012-06-28 16:37:15 +00:00
Commented Jun 28, 2012 at 16:37 — BlackVegetable
– BlackVegetable, Commented Jun 28, 2012 at 16:37

Louis Wasserman · Accepted Answer · 2012-06-28 16:37:04Z

8

The problem is that fav[s] is null.

I don't know about C#, but in Java, you have to initialize the elements of the array individually; you can't just declare the array and get it automatically filled.

You're going to have to loop through fav and fill it with new Favourite objects.

Either assign fav[s] = new Favourite() the first time you use fav[s], or initialize it all at once by doing

for (int i = 0; i < fav.length; i++) {
  fav[s] = new Favourite();
}

answered Jun 28, 2012 at 16:37

Louis Wasserman

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1 Comment

Jon Skeet Over a year ago

In C# if the OP had created a struct, it would be a value type, so the array would be full of "empty" values. That would be a bad idea for the given type, mind you - it doesn't feel like a natural value type. I will attempt to convert you to C# tomorrow ;)

David Wasser · Accepted Answer · 2012-06-28 16:38:45Z

3

Favourite[] fav = new Favourite[23]; // Allocate an array of 23 items

Now you have 23 of them!

answered Jun 28, 2012 at 16:38

David Wasser

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Comments

Carl Manaster · Accepted Answer · 2012-06-28 16:37:25Z

1

You need to put items into the array. The declared array simply has null in each slot; you need to do something like fav[s] = new Favourite().

answered Jun 28, 2012 at 16:37

Carl Manaster

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