Trouble with ArrayList

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Lawrence - 28 Nov 2006 15:50 GMT

Im relatively new to Java and have started implementing an ArrayList
using:

private ArrayList items;

initialising it using:

items = new ArrayList();

adding to it using:

items.add(item); - where item is of class Item

the problem is when i am calling the Item from the arraylist:

Item getitem = items.get(0);

I get the error message: incompatible types - Item expected but Object
found.....

Any help would be great :D

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Tobias Schröer - 28 Nov 2006 16:23 GMT

Lawrence schrieb:

> Im relatively new to Java and have started implementing an ArrayList
> using:
[quoted text clipped - 12 lines]
>
> Item getitem = items.get(0);

If you don't use generics (you don't, see your code above), you must
explicitly cast the object you get from a list:

    Item getItem = (Item)items.get(0);

Or, if you are working with Java 1.5 or above, you should use generics,
as long as you only store Item objects (or subtypes of Item) in your list:

    private ArrayList<Item> items = new ArrayList<Item>();

    items.add(item); // you can only add Item or sub types

    Item getItem = items.get(0); // now withou casting

> I get the error message: incompatible types - Item expected but Object
> found.....
>
> Any help would be great :D

HTH,
Tobi

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Doug Pardee - 28 Nov 2006 16:24 GMT

> Item getitem = items.get(0);

You need to cast the returned object to the expected type:

Item getitem = (Item) items.get(0);

Alternatively, if you're using Java 5.0 you could do it with generics:

private ArrayList<Item> items;
items = new ArrayList<Item>();
items.add(item);
Item getitem = items.get(0);

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trippy - 28 Nov 2006 21:54 GMT

In article <1164729017.173636.245310@80g2000cwy.googlegroups.com>,
Lawrence took the hamburger meat, threw it on the grill, and I said "Oh
Wow"...

> Im relatively new to Java and have started implementing an ArrayList
> using:
[quoted text clipped - 17 lines]
>
> Any help would be great :D

Cast it to the type you need.

Item itm = (Item) items.get(0);

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trippy
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"Now, technology's getting better all the time and that's fine,
but most of the time all you need is a stick of gum, a pocketknife,
and a smile."

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Trouble with ArrayList

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