File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
The moose likes Beginning Java and the fly likes Wrapping from Integer to int possible? Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login
JavaRanch » Java Forums » Java » Beginning Java
Bookmark "Wrapping from Integer to int possible?" Watch "Wrapping from Integer to int possible?" New topic

Wrapping from Integer to int possible?

Ann Smith

Joined: Apr 09, 2005
Posts: 3
After extracting the first object contained in an ArrayList, it is inevitably of type Object. I think I can cast this to an Integer (although I havent tested it, I may get a ClassCastError), and then I tried wrapping it as an int but apparently that's impossible. Any way's around this?
Chris Johnston
Ranch Hand

Joined: Dec 13, 2004
Posts: 85
I am not totally sure what you are doing here, but an int isn't an object so it can't wrap anything.

You receive an Object and you want to extract an int from it?

Should go something like this:

receive your Object
check to see if it is an instanceof Integer
parse out the int that is contained inside
Ann Smith

Joined: Apr 09, 2005
Posts: 3
Yes I realized all I had to do was use the intValue() method for Integer. I think hopefully this will solve the problem. But this is awesome because I was just looking for the method instanceOf. Where does that method come from? Which class? I need to find in stances of the same int in a List.
Steven Bell
Ranch Hand

Joined: Dec 29, 2004
Posts: 1071
instanceof is not a method it is an operator like + - * / %.

It allows you to test if an Object is of a certain type.
Ilja Preuss

Joined: Jul 11, 2001
Posts: 14112
If you are sure that the first object in the List always is an Integer, you don't need instanceof.

Use instanceof if you could get different type of objects and want to do different things with them based on their type *and* you can't use polymorphism to do it.

The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
James Carman
Ranch Hand

Joined: Feb 20, 2001
Posts: 580
Are you using JDK5? If so, you can avoid all of this by making your ArrayList an ArrayList<Integer>. Also, JDK5 will "autobox" (and "autounbox") your primitives for you, so you can avoid all of the intValue() stuff, too.

James Carman, President<br />Carman Consulting, Inc.
I agree. Here's the link:
subject: Wrapping from Integer to int possible?
It's not a secret anymore!