J2ME: perferred way to save / load data?

[Kevin]

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.

 

[Thomas Hawtin]

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?

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

 

[Kevin]

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.

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?

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

 

[AlecB]

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?

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

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.

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