In java io l'avrei fatta così :
codice:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
public class ProvaList extends JFrame{
public ProvaList(){
String prod[]={"10 PATATE","29 MELE","23 SALE","10 PERE"};
final JList lista=new JList(prod);
lista.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION );
Container cont=getContentPane();
cont.add(new JScrollPane(lista),"North");
final JLabel lab=new JLabel("Prodotti = 0");
cont.add(lab,"Center");
setBounds(100,100,200,200);
JButton but=new JButton("Calcola");
cont.add(but,"South");
but.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
Object x[]=lista.getSelectedValues();
int num=0;
for(int i=0;i<x.length;i++){
String tmp=(String)x[i];
num+=Integer.parseInt((tmp.substring(0,tmp.indexOf(" "))));
}
lab.setText("Prodotti ="+num);
}
});
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String []args){
new ProvaList().show();
}
}
Ciauz