Stuff

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Obresti
{
	public static void main(String[] args)
	{
		OFrame okno = new OFrame();
		okno.setVisible(true);
	}
}

class OFrame extends JFrame
{
	Toolkit tk = Toolkit.getDefaultToolkit();
	Dimension zaslon = tk.getScreenSize();
	
	private String naslov = "Obrestni program";
	private Container vsebina = null;
	
	private JPanel vnos = new JPanel();
	private JPanel vnos2 = new JPanel();
	private JPanel tabela = new JPanel();
	private JPanel gumbi = new JPanel();
	private JPanel gumbi2 = new JPanel();
	
	private JLabel glavnica = new JLabel();
	private JLabel obresti = new JLabel();
	private JLabel obrestiDan = new JLabel();
	
	private JTextField glavnicaIn =  new JTextField(10);
	private JTextField obrestiIn =  new JTextField(10);
	private JTextField obrestiDanIn =  new JTextField(10);
	
	private JButton izracunaj = new JButton();
	private JButton izprazni = new JButton();
	
	public OFrame()
	{
		setTitle(naslov);
		setSize(zaslon.width/2,zaslon.height/2);
  		setDefaultLookAndFeelDecorated(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		vnos.setLayout(new GridLayout(3,1,10,5));
		vnos2.setLayout(new GridLayout(3,1,10,1));
		gumbi.setLayout(new FlowLayout());
		
		glavnica.setText("Glavnica: ");
		vnos.add(glavnica);
		obresti.setText("Obresti: ");
		vnos.add(obresti);
		obrestiDan.setText("Obresti na dan: ");
		vnos.add(obrestiDan);
		
		glavnicaIn.setFocusable(true);
		vnos2.add(glavnicaIn);
		vnos2.add(obrestiIn);
		vnos2.add(obrestiDanIn);
		
		izracunaj.setText("Izracunaj");
		izracunaj.setSelected(true);
		izracunaj.addActionListener(new Poslusalec());
		gumbi.add(izracunaj);
		izprazni.setText("Izprazni");
		gumbi.add(izprazni);
				
		vsebina = getContentPane();
		vsebina.setLayout(new FlowLayout());
		vsebina.add(vnos);
		vsebina.add(vnos2);
		vsebina.add(gumbi);
	}
	
	private class Poslusalec implements ActionListener
	{
		public void actionPerformed(ActionEvent e)
		{
			Object izvor = e.getSource();
			if(izvor == izracunaj){
				int glavnicaInValue = Integer.parseInt(glavnicaIn.getText());
				int obrestiInValue = Integer.parseInt(obrestiIn.getText());
				int obrestiMesec = glavnicaInValue * (obrestiInValue/100);
				obrestiDanIn.setText(Integer.toString(obrestiMesec));
			}
			if(izvor == izprazni){
				glavnicaIn.setText("");
				obrestiIn.setText("");
				obrestiDanIn.setText("");
				glavnicaIn.setFocusable(true);
			}
		}
	}
}