Array problem

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4 total messages Started by Raul Lorenzo Thu, 25 May 2006 17:59

#194

Author: Raul Lorenzo
Date: Thu, 25 May 2006 17:59

25 lines
1450 bytes

Hello,

I have this piece of code
/***************************************************/
int index=0;
AttributeREM RoleREM[]=null;
RoleREM=new AttributeREM[asociationREM.numero_roles];
RoleREM[index].oid="hello";
/***************************************************/

Java reports me a null Pointer exception at RoleREM[index].oid="hello";
Why?
asociationREM.numero_roles is always >0

AttributeREM is a class something like this

class AttributeREM
{
public String oid;
public String name;
...
...
};

Thanks in advance

Re: Array problem

#195

Author: Lori M Olson [TeamB]
Date: Thu, 25 May 2006 20:52

54 lines
2302 bytes

Raul Lorenzo wrote:
> Hello,
> 
> I have this piece of code
> /***************************************************/
> int index=0;
> AttributeREM RoleREM[]=null;
> RoleREM=new AttributeREM[asociationREM.numero_roles];
> RoleREM[index].oid="hello";
> /***************************************************/
> 
> Java reports me a null Pointer exception at RoleREM[index].oid="hello";
> Why?
> asociationREM.numero_roles is always >0
> 
> AttributeREM is a class something like this
> 
> class AttributeREM
> {
> public String oid;
> public String name;
> ...
> ...
> };
> 
> Thanks in advance
> 

This statement:

RoleREM=new AttributeREM[asociationREM.numero_roles];

Creates an array, but it does not populate the array with instances of 
AttributeREM.  The contents of the array will all be null, until you put 
something in it.

-- 

Regards,

Lori Olson [TeamB]

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Re: Array problem

#196

Author: Raul Lorenzo
Date: Fri, 26 May 2006 13:47

40 lines
2040 bytes

Ok, It�s like C++.....I think Java create all the structure autom�tically.
Thanks

Lori M Olson [TeamB] escribi�:
> Raul Lorenzo wrote:
>> Hello,
>>
>> I have this piece of code
>> /***************************************************/
>> int index=0;
>> AttributeREM RoleREM[]=null;
>> RoleREM=new AttributeREM[asociationREM.numero_roles];
>> RoleREM[index].oid="hello";
>> /***************************************************/
>>
>> Java reports me a null Pointer exception at RoleREM[index].oid="hello";
>> Why?
>> asociationREM.numero_roles is always >0
>>
>> AttributeREM is a class something like this
>>
>> class AttributeREM
>> {
>> public String oid;
>> public String name;
>> ...
>> ...
>> };
>>
>> Thanks in advance
>>
> 
> This statement:
> 
> RoleREM=new AttributeREM[asociationREM.numero_roles];
> 
> Creates an array, but it does not populate the array with instances of
> AttributeREM.  The contents of the array will all be null, until you put
> something in it.
>

Re: Array problem

#197

Author: Alexey N. Solofnenko
Date: Sat, 27 May 2006 04:17

49 lines
2348 bytes

In Java all object variables are actually similar to C++ pointers. So, 
when you create AttributeREM* array you will also get an array of nulls.

- Alexey.

Raul Lorenzo wrote:
> Ok, It´s like C++.....I think Java create all the structure automátically.
> Thanks
> 
> Lori M Olson [TeamB] escribió:
>> Raul Lorenzo wrote:
>>> Hello,
>>>
>>> I have this piece of code
>>> /***************************************************/
>>> int index=0;
>>> AttributeREM RoleREM[]=null;
>>> RoleREM=new AttributeREM[asociationREM.numero_roles];
>>> RoleREM[index].oid="hello";
>>> /***************************************************/
>>>
>>> Java reports me a null Pointer exception at RoleREM[index].oid="hello";
>>> Why?
>>> asociationREM.numero_roles is always >0
>>>
>>> AttributeREM is a class something like this
>>>
>>> class AttributeREM
>>> {
>>> public String oid;
>>> public String name;
>>> ...
>>> ...
>>> };
>>>
>>> Thanks in advance
>>>
>> This statement:
>>
>> RoleREM=new AttributeREM[asociationREM.numero_roles];
>>
>> Creates an array, but it does not populate the array with instances of
>> AttributeREM.  The contents of the array will all be null, until you put
>> something in it.
>>

-- 
Alexey N. Solofnenko
home: http://trelony.cjb.net/

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