[ java micro ] errore compilazione

[baru]

1error : public class Hello extends MID...... segnandomi con una frecetta la parola class

is not abstract and does not override abstract method commandAction(java.microedition.lcdui.Command , javax.microedition.lcui.Displayable )

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HELP ... PLEASE

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

public class HelloJ2ME extends MIDlet implements CommandListener{

	private Display display;
    private Form fmMain;

	private Command cmExit;
	private Command cmPrimo;
    private Command cmSecondo;
    private Command cmTerzo;

	private TextBox tbAction;
	private Command cmBack;

	public HelloJ2ME(){}

    public void pauseApp(){ 
		System.out.println("In pauseApp .....\n\n"); 
        destroyApp( true ); 
		notifyDestroyed(); 
	} 
			 
	public void destroyApp( boolean unconditional ) { 
	     System.out.println("In destroyApp .....\n\n"); 
	}

	public void startApp() {     
		try {       

		display = Display.getDisplay(this);
        cmExit = new Command("Exit", Command.EXIT, 1);
        cmBack = new Command("Back", Command.BACK, 1);
		cmTerzo = new Command("Terzo", Command.SCREEN, 4);
		cmPrimo = new Command("Primo", Command.SCREEN, 2);
		cmSecondo = new Command("Secondo", Command.SCREEN, 3);

		fmMain = new Form("EuroConverter");
		fmMain.addCommand(cmExit);
		fmMain.addCommand(cmPrimo);
		fmMain.addCommand(cmSecondo);
		fmMain.addCommand(cmTerzo);
		fmMain.setCommandListener(this);
	
	       StringItem oper =new StringItem(null, "\nCreated by B.a.r.u.");
	       ImageItem lg;
	       Image logo = Image.createImage("/immicon.png");
	       lg = new ImageItem("", logo, ImageItem.LAYOUT_CENTER, "Logo");
	       fmMain.append(lg);
	       fmMain.append(oper);
	       display.setCurrent(fmMain);
	 
	     } catch (Exception e) { System.out.println("Errore!!!!"); }
	}
}