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int[] = null; help  RSS feed

 
Ranch Hand
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Hi all.
As normal how we declare a string array when we dont know the size i.e how much data should be inserted then i give as String[] str = null. After that i can perform all the operations. When i try to do the same with int that is int[] arr = null. I dont get compilation error, when i try to access its elements i am getting the java.nullpointer exception.



Any help would be greatly appreciated.
Thanks
alexander
 
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I'm not sure I understand. If you set something to null, then try to access it, of course you will get a null pointer exception. In your first example, with the String array, the same thing would happen.
 
Greenhorn
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hi..
If you want dynamic size then you can use ArrayList<String>

but it is not possible to define string array without size.
 
adeeb alexander
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Thanks for your replies guyz. See the code below. I declared a String[] temp and used it like this below. It works for me.


 
Sheriff
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That's because your giving it a value first, on line 5.
 
adeeb alexander
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yes. In the same way i have given values for int[] also. For example consider.
int [] exp= null;
for(int i = 0;i<5;i++);
{
exp[i]=i;
}

I have to do somewhat this thing in my program also.

when i use System.out.println(exp[0]);

i get error during execution. i need the reason please. As you said i have given values to exp isnt it?


Thanks
 
Rob Spoor
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You don't assign anything to exp itself. Nowhere are you calling "exp = X" where X is something other than null. That means that the array itself remains null, and there are no elements to access.

With the String[] you are doing just that and that's why that example is working and this one isn't.

The easiest solution is adding "exp = new int[5];" just before the loop.
 
adeeb alexander
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Hi
Look at the code below. I am using this to solve given input separated by ",". I think i have used some extra code. i.e i guess there is some other short way to do this. If any one know please share with me.


Thanks and Regards
alexander
>
 
It is sorta covered in the JavaRanch Style Guide.
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