J2ME RecordStore Example

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.rms.RecordEnumeration;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms.RecordStoreException;

/**
* Preferences Store
*
*Create a class that can persist program preferences. The class will store the preferences into a Record Store.
*Each record will have a variable name and value. Each variable/value pair is stored in a single record.
*The name and value are stored in the database as Strings.
*
*The class should implement these methods:
*public String readVar(RecordStore recStore, String name, String defaultValue)
*public void writeString(RecordStore recStore, String name, String value);
*
* @author calcifer
*
*/

public class PreferenceStore extends MIDlet implements CommandListener{
private Display display;
private Command exit;
private Command write;
private Command read;
private Command back;

private Form inputForm;

private TextBox output = new TextBox("Your Preference:", "", 250, TextField.ANY);
private TextField varName = new TextField("VarName:", "",32,TextField.ANY);
private TextField varValue = new TextField("Value:", "", 32,TextField.ANY);

private RecordStore recStore;

private Alert success;

public PreferenceStore(){
inputForm = new Form("Preference");

exit = new Command("Exit",Command.EXIT, 0);
write = new Command("Write", Command.OK, 0);
read = new Command("Read", Command.OK, 0);
back = new Command("Back", Command.BACK, 0);

output.addCommand(back);
output.setCommandListener(this);

inputForm.append(varName);
inputForm.append(varValue);
inputForm.addCommand(exit);
inputForm.addCommand(write);
inputForm.addCommand(read);
inputForm.setCommandListener(this);

success = new Alert("","Successfully Added!", null, AlertType.INFO);

}

public void startApp() {
try {
recStore = RecordStore.openRecordStore("Preferences", true);
} catch (RecordStoreException ex) {
ex.printStackTrace();
} catch (Exception e){
e.printStackTrace();
}
if(display == null){
display = Display.getDisplay(this);
}
display.setCurrent(inputForm);
}

public void pauseApp() {
}

public void destroyApp(boolean unconditional) {
}

public void commandAction(Command c, Displayable d){
if(c == exit){
notifyDestroyed();
try{
recStore.closeRecordStore();
}catch(Exception e){e.printStackTrace();}
}
else if(c == write){
display.setCurrent(success);
writeString(recStore, varName.getString(), varValue.getString());
varName.setString("");
varValue.setString("");
}
else if(c == read){
output.setString("");
output.setString(readVar(recStore, varName.getString(), varValue.getString()));
display.setCurrent(output);
varName.setString("");
varValue.setString("");
}
else if(c == back){
display.setCurrent(inputForm);
}
}

public void writeString(RecordStore recStore, String name, String value){
String newItem = new String(name + value);

byte[] bytes = newItem.getBytes();
try{
recStore.addRecord(bytes, 0, bytes.length);
}catch(Exception e){ e.printStackTrace();}
}

public String readVar(RecordStore recStore, String name, String defaultValue){
StringBuffer sb = new StringBuffer();

try{
RecordEnumeration enumerator = recStore.enumerateRecords(null, null, true);
while(enumerator.hasNextElement()){
String item = new String(enumerator.nextRecord());
String val = new String(name + defaultValue);
if(item.equals(val))
sb.append(item);
}

}catch(Exception e){e.printStackTrace();}

return sb.toString();
}

}