import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.GeneralPath;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Sine {
    final double X_MIN = -2*Math.PI;
    final double X_MAX = 2*Math.PI;

    final double Y_MIN = -1.2;
    final double Y_MAX = 1.2;

    final double X_SHIFT      = 0.2;
    final long   X_SHIFT_TIME = 50; //ms

    final double N_POINTS = 1000;
    final double DX    = (X_MAX-X_MIN)/(double) N_POINTS;

    GeneralPath path;

    private final Object lock = new Object();

    final JPanel panel = new JPanel(){
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            Graphics2D g2 = (Graphics2D) g;

            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);

            g2.setPaint(Color.BLACK);
            // x axis
            g2.drawLine(0, (int) toCanvasY(0), panel.getWidth(), (int) toCanvasY(0));
            // y axis
            g2.drawLine((int) toCanvasX(0), 0, (int) toCanvasX(0), panel.getHeight());


            g2.setPaint(Color.RED);
            synchronized(lock) {
                if(path != null) g2.draw(path);
            }
        }
    };

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            Sine sine = new Sine();

            sine.createAndShowGUI();

            sine.start();
        });
    }

    void createAndShowGUI() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("Sine wave");

        panel.setBackground(Color.WHITE);

        frame.add(panel);
        frame.setSize(500,300);
        frame.setVisible(true);
    }

    void start() {
        Thread th = new Thread(() -> {
            long count = 0;

            while( true ) {
                fillPath(count++ * X_SHIFT);
                panel.repaint();

                try {
                    Thread.sleep(X_SHIFT_TIME);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
        th.setDaemon(true);

        th.start();
    }

    void fillPath(double xShift) {
        GeneralPath p = new GeneralPath();

        p.moveTo(toCanvasX(X_MIN), toCanvasY(Math.sin(X_MIN + xShift)));

        for(int i=1; i<=N_POINTS; i++) {
            double x = X_MIN + DX * i;
            double y = Math.sin(x + xShift);

            p.lineTo(toCanvasX(x), toCanvasY(y));
        }

        synchronized(lock) {
            path = p;
        }
    }

    double toCanvasX(double x) {
        double wPanel = (double) panel.getWidth();
        double xw = X_MAX - X_MIN;

        return (x+(xw/2))*(wPanel/xw);
    }

    double toCanvasY(double y) {
        double hPanel = (double) panel.getHeight();
        double yh = Y_MAX - Y_MIN;

        return (-y+(yh/2))*(hPanel/yh);
    }

}