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 Arraylist contains this number? Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of Java Interview Guide this week in the Jobs Discussion forum!
JavaRanch » Java Forums » Java » Beginning Java
Bookmark "Arraylist contains this number?" Watch "Arraylist contains this number?" New topic

Arraylist contains this number?

jonas sorensen

Joined: Jan 23, 2013
Posts: 1
Hello people.
Srry for asking, but i've been trying for the last four hours and i'm not moving forward.

I'm programming this bingo thing. It has to check if a number exists in the arraylist. If it does, it should get a new number NytTal();

I've also tried with equals, but dosent seem to work either. I've made an system outprint;

[80, 11, 14, 14]
Equals: false
Contains: false

I've even tried with bought trukkettal and trukkettal2

what seems to be wrong here? i just have a simple arraylist and then some adds from actionperformed...

Tony Docherty

Joined: Aug 07, 2007
Posts: 2839
Your ArrayList is declared as containing String values but your if statement is checking if the ArrayList contains an Integer (the int value will be AutoBoxed to an Integer).
Campbell Ritchie

Joined: Oct 13, 2005
Posts: 46427
Welcome to the Ranch

I am afraid your five lines of code fill me with dread. And not about finding things in the List.
Why are you using a method which returns a String and parsing it to a number? Why did you not return a number?
Why are you trying to put things into a List, and then check whether they have already been added?
Why are you calling that code from a Listener? Why are you not developing it as a standalone application, which you will later wrap in a GUI? That is a far better way to develop applications. Your application should have an interface so you can do something like this:-I think there is a piece of hardware getting between you and the program. Unfortunately it is the computer, and I think you will have to put it aside. Instead, use a two‑dimensional carbohydrate‑based flexible writing surface¹.
Write down how you would do it is real life, with a bag of balls. See whether you can change the bag of balls to a Java collections implementation. I presume you are familiar with the random number methods in Java? (They are not really random, but you won’t notice the difference.)

¹ = sheet of paper
Winston Gutkowski

Joined: Mar 17, 2011
Posts: 8954

jonas sorensen wrote:It has to check if a number exists in the arraylist.

OK, but, as Tony said, that's NOT what you're doing.

Strings are NOT numbers. In fact, in your case (and many others) StringsAreBad (←click).


Bats fly at night, 'cause they aren't we. And if we tried, we'd hit a tree -- Ogden Nash (or should've been).
Articles by Winston can be found here
I agree. Here's the link:
subject: Arraylist contains this number?
It's not a secret anymore!