I've painted myself into a bit of a corner. Havning finally really wrapped my head around the handiness and functionality of references, I designed a data structure which is quite elegant... or at least clear and functional for my purposes.

To make this as simple as possible -- I've got two classes A and B. When I load a midi file, the data from the midi file is organized into a number of A objects and a number of B objects. A objects basically contain vertical data (harmony), while B objects contain horizontal data (motives). The A objects hold references to B objects, and vice versa.

I'm trying to save all this data in a file. In order to access the data, I've loaded all of the A objects from an analyzed midi file into a HashMap: Map. However, when I save Map, it appears that the actual data from the B objects gets left behind -- if I query the B data from a loaded Map file, I get NullPointerExceptions, suggesting that there's no B data stored. Because the A objects are actually loaded to the Map and saved, all of the A object data appears to be intact.

So, how can I save the Map in such a way as to also save the referenced B data?

Does that question make any sense? Is this Java 101?

I'm trying to save all this data in a file. In order to access the data, I've loaded all of the A objects from an analyzed midi file into a HashMap: Map. However, when I save Map, it appears that the actual data from the B objects gets left behind -- if I query the B data from a loaded Map file, I get NullPointerExceptions, suggesting that there's no B data stored. Because the A objects are actually loaded to the Map and saved, all of the A object data appears to be intact. 

misguided-planning

Sounds like you may have to make B implement the serializable 

mechanism to serialize your objects to disk.

On Jan 21, 2007, at 17:30 PM, jbmaxwell wrote:

> I've painted myself into a bit of a corner. Havning finally really 

> wrapped my head around the handiness and functionality of 

> references, I designed a data structure which is quite elegant... 

> or at least clear and functional for my purposes.

> To make this as simple as possible -- I've got two classes A and B. 

> When I load a midi file, the data from the midi file is organized 

> into a number of A objects and a number of B objects. A objects 

> basically contain vertical data (harmony), while B objects contain 

> horizontal data (motives). The A objects hold references to B 

> I'm trying to save all this data in a file. In order to access the 

> data, I've loaded all of the A objects from an analyzed midi file 

> into a HashMap: Map. However, when I save Map, it appears that the 

> actual data from the B objects gets left behind -- if I query the B 

> data from a loaded Map file, I get NullPointerExceptions, 

> suggesting that there's no B data stored. Because the A objects are 

> actually loaded to the Map and saved, all of the A object data 

> So, how can I save the Map in such a way as to also save the 

> Does that question make any sense? Is this Java 101?

Sounds like you may have to make B implement the serializable  
interface or come up with your own
mechanism to serialize your objects to disk.
topher

>
> Help!
>
> I've painted myself into a bit of a corner. Havning finally really  
> wrapped my head around the handiness and functionality of  
> references, I designed a data structure which is quite elegant...  
> or at least clear and functional for my purposes.
>
> To make this as simple as possible -- I've got two classes A and B.  
> When I load a midi file, the data from the midi file is organized  
> into a number of A objects and a number of B objects. A objects  
> basically contain vertical data (harmony), while B objects contain  
> horizontal data (motives). The A objects hold references to B  
> objects, and vice versa.
>
> I'm trying to save all this data in a file. In order to access the  
> data, I've loaded all of the A objects from an analyzed midi file  
> into a HashMap: Map. However, when I save Map, it appears that the  
> actual data from the B objects gets left behind -- if I query the B  
> data from a loaded Map file, I get NullPointerExceptions,  
> suggesting that there's no B data stored. Because the A objects are  
> actually loaded to the Map and saved, all of the A object data  
> appears to be intact.
>
> So, how can I save the Map in such a way as to also save the  
> referenced B data?
>
> Does that question make any sense? Is this Java 101?
>
> J.
>
>


Quote: topher lafata wrote on Sun, 21 January 2007 17:56

----------------------------------------------------

> Sounds like you may have to make B implement the serializable 

> mechanism to serialize your objects to disk.

Yeah, you know, guided by exception.toString() messages, I figured out the Serializable stuff, but it still doesn't seem to be working. In the meantime I read up on this general problem, and the Serializable interface does seem to be the answer. So, I made my A and B classes both serializable, but I'm still getting empty B objects in my Map.

Since A seems okay, I'm taking a closer look at B. Thanks, Topher.

Quote: topher lafata wrote on Sun, 21 January 2007 17:56
----------------------------------------------------
> Sounds like you may have to make B implement the serializable  
> interface or come up with your own
> mechanism to serialize your objects to disk.
> topher
>

Yeah, you know, guided by exception.toString() messages, I figured out the Serializable stuff, but it still doesn't seem to be working. In the meantime I read up on this general problem, and the Serializable interface does seem to be the answer. So, I made my A and B classes both serializable, but I'm still getting empty B objects in my Map. 

Misguided planning.