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Complete novice question

Tony Gormley
Greenhorn

Joined: Oct 28, 2003
Posts: 3
Hi,
its the first time I have posted here. I am just starting with JAVA and really need some help with a small prgram I have writtem I was messing about so the progrm will probably look a bit dtrange and pointless but the whole point was really just to create an Array, populate it with data and search succesfully on one of the variables. The problem is at the very bottom, I just cant figure out where i am going wrong.
Here is the code

The text file
32 Glasgow 12
George Stephenson
44 Edinburgh 15
Robert McMeachan
21 London 20
John Smith
22 Rochdale 21
Richard Evans
23 Lisbon 23
Frank White
24 Lisboa 250
Gerry McNee
25 Azoia 33
Randall Hopkins
28 Cascais 45
Telly Savallas
56 Estoril 50
Randy Hopkins
============================================================================
And finally the error message!
java.lang.NullPointerException
at Person2.main(Person2.java:59)
Exception in thread "main"
============================================================================
I know I am doing something wrong but cant figure exactly what, any help would be greatly appreciated!
Thanks in advance.

[ edited to format code -ds ]
[ October 31, 2003: Message edited by: Dirk Schreckmann ]
William Barnes
Ranch Hand

Joined: Mar 16, 2001
Posts: 984

Please use *code* tags.
Place a comment on the line which is breaking.
Don't include lines of code which are commented out,
and ... I think someone else is posting questions about this exact same assignment. Check the other posts.


Please ignore post, I have no idea what I am talking about.
Carl Pettersson
Ranch Hand

Joined: Sep 09, 2003
Posts: 73
William, believe it or not, it's not the same thing that I have been pestering everyone with Funny thing that we got assignments looking so alike
Tony Gormley
Greenhorn

Joined: Oct 28, 2003
Posts: 3
Hi,
thanks for the reply, can I just say to begin with, if this was a homewrok assignment I would be honest enough to say so, beleive it or not I actually want to learn how to do this. Sorry about the code tags didnt realise about that, so heres the code


Here is the error exactly as it appears,
java.lang.ArrayIndexOutOfBoundsException
at personList.getPersonAt(personList.java:77)
at Person2.main(Person2.java:54)
Exception in thread "main"
If i can get a handle on how to this I should be able to work with Arrays a bit better than just now. And apologies if I have messed up again, I appreciate the patience of your good selves with programming novice!
Cheers.
[ edited to fix formatting -ds ]
[ October 31, 2003: Message edited by: Dirk Schreckmann ]
William Barnes
Ranch Hand

Joined: Mar 16, 2001
Posts: 984

Couple of things. You can get around this error by checking for MAX in that method, and or catching that exception. But I would first recommand making a method to dump all of your data. Make it a private method and only use it for debugging purposes.
And just add a bunch of print statements everywhere - the poor mans debugger. Printing out the number of the index which is killing that method would be a good one.
I am assuming you know why the programming is dieing. Ok, in case you don't. You are asking for an element in the array which doesn't exist. You would get this error if for example you have an array with 10 elements and you want to do something with element number 11.
Tony Gormley
Greenhorn

Joined: Oct 28, 2003
Posts: 3
damn messed up the last bit of code
here its again

and the error
java.lang.ArrayIndexOutOfBoundsException
at personList.getPersonAt(personList.java:77)
at Person2.main(Person2.java:54)
Exception in thread "main"
Thanks :roll:
William Barnes
Ranch Hand

Joined: Mar 16, 2001
Posts: 984

Not sure why you are re-posting you code.
My comments are just general comments which will help you find the problem. So look at my last post.
What is the difference between getPosition() and getPersonAt(). It can be rather confusing to have two different methods doing the same thing.
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: Complete novice question
 
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