Programming Tutorials

How to get the CLDC and MIDP version from a J2ME program

By: Ivan Lim  

The CLDC/MIDP supports system properties, which are key-value pairs that represent information about the platform and environment in which MIDP applications execute. Conceptually these are the same type of properties that you find in J2SE. Unfortunately, there is no java.util.Properties class in CLDC/MIDP to facilitate your handling of properties.

The MIDP specification defines only a small set of standard properties, which are shown in Table
3.4. Implementations may support additional, manufacturer-specific system properties, but these
are nonstandard. You should be aware of what manufacturer- or platform-specific features you use
in order to anticipate portability issues.
Like J2SE applications, MIDP applications can retrieve a system property using the
java.lang.System class. To retrieve the value of a property, use the System class method
String getProperty(String key)
This method retrieves the property value associated with the key whose value is specified in the
call.

Standard CLDC System Properties

  A sample J2ME program illustrates the retrieval of system properties in a MIDlet.

MIDlets have direct access to all four of the standard system properties defined by the CLDC specification.
 
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.midlet.MIDlet;
/**
Creates the "Hello world" program in J2ME MIDP.
Note that the class must be public so that the device
application management software can instantiate it.
*/
public class HelloWorld extends MIDlet
{
...
public void startApp()
{
// Create a Displayable widget.
form = new Form("Hello World");
// Add a string to the form.
String msg = "My first MIDlet!";
form.append(msg);
// This app simply displays the single form created
// above.
display = Display.getDisplay(this);
display.setCurrent(form);
printSystemProperties();
}
/**
Prints the values of the standard system properties
using the System.getProperty() call.
*/
protected void printSystemProperties()
{
String conf;
String profiles;
String platform;
String encoding;
String locale;
conf = System.getProperty("microedition.configuration");
System.out.println(conf);
profiles = System.getProperty("microedition.profiles");
System.out.println(profiles);
platform = System.getProperty("microedition.platform");
System.out.println(platform);
encoding = System.getProperty("microedition.encoding");
System.out.println(encoding);
locale = System.getProperty("microedition.locale");
System.out.println(locale);
System.out.println();
}
 
}

Notice the addition of the call to the method printSystemProperties() at the end of the startApp() method. This method simply retrieves and prints to standard output the values of the five standard MIDP system properties. The data that the program writes to standard output is shown next:\

CLDC-1.0
MIDP-1.0
j2me
ISO-8859-1
en_US

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