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Applet giving NullPointerException?

 
Nitesh Panchal
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why does this applet throws NullPointerException? infact whenever i use for loop in init() the applet doesn't run in appletviewer. I am using Windows XP SP2. Here's the code
i am trying to create a space. Here's the code



I think i have allocated memory for every object that i am going to use then why this NullPointerException. I am breaking my head since 1 hour in vain (I've allocated memory for 1000 objects but i am using only 1st object, but i guess that shouldn't be the problem)
Please tell me the reason for this weird behaviour of applet
 
pete stein
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You forgot to create a new instance of each object in the array that you use:
 
Nitesh Panchal
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But why again allocate the memory for individual objects?
I mean i allocated memory for 1000 objects altogether. Didn't i?



please tell me what does the above statement do?
 
pete stein
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chotta chatri wrote:But why again allocate the memory for individual objects?
I mean i allocated memory for 1000 objects altogether. Didn't i?

No



please tell me what does the above statement do?

It initializes an array object but does not initialize the array items. You have to do that yourself as I demonstrated.
 
Nitesh Panchal
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so you have to do that this way only for every class?i mean say for String class i want to allocate memory for 10 objects

do i have to do it this way?


or this way?



>
 
pete stein
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chotta chatri wrote:so you have to do that this way only for every class?i mean say for String class i want to allocate memory for 10 objects

do i have to do it this way?


String is an exception as you construct a String object (if necessary) by simply assigning a String literal to a variable. So otherwise, yes, you have to do this for any array of objects. Now this is not necessary for an array of primitives since they don't have to be constructed.
 
Nitesh Panchal
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Right! thanks you're the man
Now concept's getting clearer in my mind. Actually i am pretty new to Java and i knew how to allocate memory for primitive type array but memory for user defined class i didn't know that you have to do it this way!
 
pete stein
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chotta chatri wrote:Right! thanks you're the man
Now concept's getting clearer in my mind. Actually i am pretty new to Java and i knew how to allocate memory for primitive type array but memory for user defined class i didn't know that you have to do it this way!

Good. Glad you've got it straight now. Just curious though, what are you trying to draw here? an orbit of some sort? Your image is off the screen, you know. Also, why choose to use AWT and not the more recent, flexible, and powerful Swing?
 
Nitesh Panchal
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Yeah orbit sort of things in which "circles" pop up from the space and keep revolving i am trying to figure out why is it going out of screen.
Yeah Swing is powerful but in our college course it's AWT no Swing ,in our course so i can't retialiate and ask them to keep Swing even though this is the most recent
 
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