Exemplo de Midlet

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class HelloWorld extends MIDlet {
  private boolean paused;
  private Display myDisplay;
  private HelloCanvas myCanvas;

  public HelloWorld() {
    paused = false;
  }

  public void startApp() throws MIDletStateChanged {
  // Check if this is the first time the application runs or  
  // if the VM resumed the app from paused state
    if( paused ) {
      //resume from paused state
      myCanvas.repaint();
    }  
    else {
      // first run, create forms
      myDisplay = Display.getDisplay( this );
      myCanvas = new HelloCanvas();
      myDisplay.setCurrent( myCanvas );
    }
  }

  public void pauseApp() {
    //prepare for pausing the app
    paused = true;
    notifyPaused();
  }

  public void destroyApp( boolean unconditional ) {
    //clean up
    // notify the system that we're ready for destruction
    notifyDestroyed();
  }

  class HelloCanvas extends Canvas {

    public void paint( Graphics g ) {
      //Set color to white
      g.setColor( 0x0FFFFFF );
      //Fill entire screen
      g.fillRect( 0, 0, getWidth(), getHeight() );
      //Set color to black
      g.setColor( 0 );
      if( paused ) {
        paused = false;
        g.drawString("Welcome back", 0, 0, Graphics.TOP |     
                      Graphics.LEFT );
      }
      else {
        g.drawString("Hello World", 0, 0, Graphics.TOP | 
                      Graphics.LEFT );
      }
    }
  }
}