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

public class Kalkulator {
	JFrame ramme;
	JPanel ovrePanel;
	JPanel nedrePanel;
	
	JLabel tall;
	JButton[] numKnapper;
	JButton[] spesKnapper;
	KnappeLytter lytter;
	
	int mellomlager;
	
	public Kalkulator() {
		// Oppretter ramme og paneler
		ramme = new JFrame("KALKULATOR");
		ovrePanel = new JPanel();
		nedrePanel = new JPanel();
		
		// Ordner ovre panel
		tall = new JLabel();
		ovrePanel.add(tall);
		
		// Lager knappe-arrays
		numKnapper = new JButton[9];
		spesKnapper = new JButton[3];
		lytter = new KnappeLytter();
		
		for(int i = 0; i < numKnapper.length; i++) {
			numKnapper[i] = new JButton("" + (i+1));
			numKnapper[i].addActionListener(lytter);
		}
		
		for(int i = 0; i < spesKnapper.length; i++) {
			spesKnapper[i] = new JButton();
			spesKnapper[i].addActionListener(lytter);
		}
		
		spesKnapper[0].setText("+");
		spesKnapper[1].setText("=");
		spesKnapper[2].setText("0");
		
		// Legge knapper paa nedre panel
		nedrePanel.setLayout(new GridLayout(3, 4));
		
		int spesTeller = 0;
		int tallTeller = 0;
		
		for(int i = 0; i < 12; i++) {
			if((i+1) % 4 == 0) {
				nedrePanel.add(spesKnapper[spesTeller++]);
			} else {
				nedrePanel.add(numKnapper[tallTeller++]);
			}
		}
		
		// Setter paneler paa ramme
		ramme.setLayout(new BorderLayout());
		ramme.add(ovrePanel, BorderLayout.NORTH);
		ramme.add(nedrePanel, BorderLayout.SOUTH);
		
		// Standard ramme-operasjoner
		ramme.setSize(300, 300);
		ramme.setVisible(true);
		ramme.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	
	private class KnappeLytter implements ActionListener {
		public void actionPerformed(ActionEvent e) {
			for(int i = 0; i < numKnapper.length; i++) {
				if(e.getSource() == numKnapper[i]) {
					tall.setText(tall.getText() + (i+1));
				}
			}
			
			if(e.getSource() == spesKnapper[0]) {
				mellomlager = Integer.parseInt(tall.getText());
				tall.setText("");
			} else if (e.getSource() == spesKnapper[1]) {
				int resultat = mellomlager + Integer.parseInt(tall.getText());
				tall.setText(resultat + "");
			} else if (e.getSource() == spesKnapper[2]) {
				tall.setText(tall.getText() + 0);
			}
		}
	}
}