Explain me how the tone method is working

See more:

Java

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.SourceDataLine;

/**
 * @dev :   devpar
 * @date :   03-May-2021
 */

public class Sound
{
    public static float SAMPLE_RATE = 8000f;
    public static void tone(int hz, int msecs)
            throws LineUnavailableException
    {
        tone(hz, msecs, 1.0);
    }

    public static void tone(int hz, int msecs, double vol)
            throws LineUnavailableException
    {
        byte[] buf = new byte[1];
        AudioFormat af = new AudioFormat(SAMPLE_RATE,8,1,true,false);
        SourceDataLine sdl = AudioSystem.getSourceDataLine(af);
        sdl.open(af);
        sdl.start();
        for (int i=0; i < msecs*8; i++) {
            double angle = i / (SAMPLE_RATE / hz) * 2.0 * Math.PI;
            buf[0] = (byte)(Math.sin(angle) * 127.0 * vol);
            sdl.write(buf,0,1);
        }
        sdl.drain();
        sdl.stop();
        sdl.close();
    }

    public static void main(String[] args) throws Exception {
        Sound.tone(15000,1000);
    }
}

What I have tried:

I would like to understand how the tone method inside sound class is working.
Most of the things goes above from my head and could not understand the source.

link for the above source