Q:

Java basic paint program ugly brush

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

public class Circle extends JPanel {
private final ArrayList<Point> point = new ArrayList<>();

public Circle() {
    addMouseListener(new MouseAdapter() {
        public void mousePressed(MouseEvent event) {
            point.add(event.getPoint());
            repaint();
        }
    });

    addMouseMotionListener(new MouseMotionAdapter() {
        public void mouseDragged(MouseEvent event) {
            point.add(event.getPoint());
            repaint();
        }
    });
}

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(new Color(0, 0, 128));
    for (Point p : point)
        g.fillOval(p.x, p.y, 15, 15);
}

public static void main(String[] args) {
    JFrame f = new JFrame();
    f.add(new Circle());
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setSize(800, 600);
    f.setVisible(true);
}
}

Here is sample program.
Drawing it display ugly gap:

I looked many tutorials for java paint, but everytime their explanation is like the above sample program. How can Java make smooth brush style like Microsoft Paint?

A:

You need to draw lines between the points instead of ovals at each point. Here's a slightly modified paintComponent method:
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;
    g2.setColor(new Color(0, 0, 128));
    g2.setStroke(new BasicStroke(15f,
                                 BasicStroke.CAP_ROUND,
                                 BasicStroke.JOIN_ROUND));
    for (int i = 1; i < point.size(); i++)
        g2.draw(new Line2D.Float(point.get(i-1), point.get(i)));
}

Result:

