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HeX · Jun 3rd, 2005, 8:23 AM

I am writing an appointment manager. The first frame of the program has 31 buttons (days of a month), when I click a day, another frame shows the appointments made on that day. I made it so that the appointments titles are shown in a JList, and then if you click in a title another frame comes out and shows the description of that appointment.
I also wrote a class Database in which the titles and descritpions of the appointments are stored in a two-dimensional array (ie. descritpion[day][title]).
The problem is that when the program executes the first time, after I click on a day of the month, it thrws a Null Pointer Exception, because the JList takes the titles from the database, and when it is executed the first time, the database is empty.

Any suggestion how to avoid this?

OpenLoop · Jun 3rd, 2005, 9:59 AM

put a dummy record in the database or initialize the array to " ".
you can also use exception handling
i don't know if its the same in java but in c#:

(Toggle Plain Text)

try{
//the code that throws the exception goes here
}
catch(Exception ex)
{
//do something to handle the exception
}

i hope this helps

Knight · Jun 4th, 2005, 9:49 PM

Thats right, OpenLoop, for the Java code. It may be a good practice to start initializing the variables to something when you declare them (atleast for me, I find it very handy)

Jun 3rd, 2005, 8:23 AM	#1
HeX Programmer Join Date: May 2005 Location: Kosova Posts: 94 Rep Power: 4	Null Pointer Exception I am writing an appointment manager. The first frame of the program has 31 buttons (days of a month), when I click a day, another frame shows the appointments made on that day. I made it so that the appointments titles are shown in a JList, and then if you click in a title another frame comes out and shows the description of that appointment. I also wrote a class Database in which the titles and descritpions of the appointments are stored in a two-dimensional array (ie. descritpion[day][title]). The problem is that when the program executes the first time, after I click on a day of the month, it thrws a Null Pointer Exception, because the JList takes the titles from the database, and when it is executed the first time, the database is empty. Any suggestion how to avoid this? __________________ (Toggle Plain Text) countdown++; countdown++;

Jun 3rd, 2005, 9:59 AM	#2
OpenLoop Expert Programmer Join Date: May 2005 Location: East Lansing, MI Posts: 663 Rep Power: 4	put a dummy record in the database or initialize the array to " ". you can also use exception handling i don't know if its the same in java but in c#: (Toggle Plain Text) try{ //the code that throws the exception goes here } catch(Exception ex) { //do something to handle the exception } try{ //the code that throws the exception goes here } catch(Exception ex) { //do something to handle the exception } i hope this helps

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Jun 4th, 2005, 9:49 PM	#3
Knight Newbie Join Date: Jun 2005 Posts: 28 Rep Power: 0	Thats right, OpenLoop, for the Java code. It may be a good practice to start initializing the variables to something when you declare them (atleast for me, I find it very handy)

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