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Accessing Record Stores with the RecordStore Class

The RecordStore class is the developer's interface to the underlying RMS. Record stores are created in a platform-dependent manner by the midlet environment. Actual locations and storage information are hidden from the application developer. Instead, record stores can be accessed using a simple naming convention: Names can be up to 32 Unicode characters long, are case sensitive, and must be unique within a midlet suite (a collection of midlets and resources bundled together in a compressed JAR file). All midlets within a midlet suite have read/write access to a record store, assuming they know the correct name. Should that midlet suite be removed from the device, all record stores associated with that suite will also be deleted.

To open a record store named TestRecordSet, for example, you call the RecordStore.openRecordStore() method. This method takes two arguments: a string indicating the record store name, and a Boolean that—if true—will create the record store if it doesn't already exist. To create our new TestRecordSet record store, we make the following method calls:

RecordStore rs = null;
rs = RecordStore.openRecordStore("TestRecordSet", true);

After this record store has been created, we can add data to the record store by calling the RecordStore.addRecord() method. addRecord() accepts three arguments:

Argument

Description

byte[] data

An array of byte data to be stored in this record. Typically, data is added to the byte array via the java.io.ByteArrayOutputStream and java.io.DataOutputStream classes.

int offset

The index into the data buffer of the first relevant byte of this record.

int numBytes

The number of bytes of the data buffer to use for this record.

On successful completion of the addRecord() call, the method returns an integer specifying the ID of the record in the record store. Although I won't use them in my examples in this article, RecordStore also specifies other data editing methods, including setRecord() and deleteRecord().

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