package zadanko;

import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;

class Surface extends JPanel {

    private void doDrawing(Graphics g) {

        Graphics2D g2d = (Graphics2D) g;

        g2d.drawLine(60, 30, 200, 30);
        g2d.drawLine(60, 200, 200, 200);
        g2d.drawLine(60, 30, 60, 200);
        g2d.drawLine(200, 30, 200, 200);
        g2d.drawLine(60, 30, 130, 5);
        g2d.drawLine(200, 30, 130, 5);


    }

    @Override
    public void paintComponent(Graphics g) {

        super.paintComponent(g);
        doDrawing(g);
    }
}

public class Zadanko extends JFrame {

    public Zadanko() {

        initUI();
    }

    private void initUI() {

        add(new Surface());

        setTitle("Lines");
        setSize(600, 400);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {

                Zadanko ex = new Zadanko();
                ex.setVisible(true);
            }
        });
    }
}