J2ME: perferred way to save / load data?

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Kevin - 06 Jul 2006 21:31 GMT

Hi,

I am pretty new to J2ME, can anyone give some hits of the good ways to
save / load data on these mobile devices using J2ME? Thanks a lot.

The way I currently know is:
to use the javax.microedition.rms.RecordStore
But it only handles byte[] arrays.
How about int, double, and Date (object)?
I know I can convert int and double to byte[], but not Date. (also,
this sounds not good).

Or, we can just use a file with java.io.DataInputStream like those in
normal j2se?

Any performance issues there?

Thanks a lot.

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Thomas Hawtin - 06 Jul 2006 21:49 GMT

> I am pretty new to J2ME, can anyone give some hits of the good ways to
> save / load data on these mobile devices using J2ME? Thanks a lot.
[quoted text clipped - 8 lines]
> Or, we can just use a file with java.io.DataInputStream like those in
> normal j2se?

The obvious way to do it is with Data(In|Out)putStream feeding to a
ByteArray(In|Out)putStream.

Date can be converted into a long with getTime.

Tom Hawtin

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Unemployed English Java programmer
http://jroller.com/page/tackline/

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Kevin - 06 Jul 2006 23:11 GMT

So we must convert all these int (4 bytes), double (8 bytes), long (8
bytes) to byte[] arrays? Sounds not like a decent idea.......

How about to use the java.io.DataInputStream? I heard it may not have
good performance.

By the way, for RecordStore, is the get record by ID a "random access"
to the underlying file? Will the system hold all the records in memory?

Thanks all. :-)

> > I am pretty new to J2ME, can anyone give some hits of the good ways to
> > save / load data on these mobile devices using J2ME? Thanks a lot.
[quoted text clipped - 18 lines]
> Unemployed English Java programmer
> http://jroller.com/page/tackline/

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AlecB - 07 Jul 2006 00:25 GMT

>>> I am pretty new to J2ME, can anyone give some hits of the good ways to
>>> save / load data on these mobile devices using J2ME? Thanks a lot.
[quoted text clipped - 28 lines]
>
> Thanks all. :-)

IFYP.

The recordstore can be accessed randomly. Be careful though, if you
perform deletes, the id of the first record will not be 1, which means
using a recordstore enumeration.

Data(In|Out)putStreams are very slow on certain devices. I recommend
only using them when you absolutely have to. you can usually do the
conversion yourself.

Regards,
Alec

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J2ME: perferred way to save / load data?

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