Java Graphics How to - Draw sine curve

Question

We would like to know how to draw sine curve.
Answer

//from ww w.j  a v a  2 s  . co  m
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

class SineDraw extends JPanel {
    private static final int SCALEFACTOR = 200;

    private int cycles;

    private int points;

    private double[] sines;

    private int[] pts;

    public SineDraw() {
        setCycles(5);
    }

    public void setCycles(int newCycles) {
        cycles = newCycles;
        points = SCALEFACTOR * cycles * 2;
        sines = new double[points];
        for (int i = 0; i < points; i++) {
            double radians = (Math.PI / SCALEFACTOR) * i;
            sines[i] = Math.sin(radians);
        }
        repaint();
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        int maxWidth = getWidth();
        double hstep = (double) maxWidth / (double) points;
        int maxHeight = getHeight();
        pts = new int[points];
        for (int i = 0; i < points; i++)
            pts[i] = (int) (sines[i] * maxHeight / 2 * .95 + maxHeight / 2);
        g.setColor(Color.RED);
        for (int i = 1; i < points; i++) {
            int x1 = (int) ((i - 1) * hstep);
            int x2 = (int) (i * hstep);
            int y1 = pts[i - 1];
            int y2 = pts[i];
            g.drawLine(x1, y1, x2, y2);
        }
    }
}

public class Main extends JPanel {
    private SineDraw sines = new SineDraw();

    private JSlider adjustCycles = new JSlider(1, 30, 5);

    public Main() {
      super(new BorderLayout());
        add(BorderLayout.CENTER,sines);
        adjustCycles.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent e) {
                sines.setCycles(((JSlider) e.getSource()).getValue());
            }
        });
        add(BorderLayout.SOUTH, adjustCycles);
    }

    public static void main(String[] args) {
        JPanel p = new Main();
    
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(p);
        frame.setSize(500,500 );

        frame.setVisible(true);
    }
}