public class AudioVisualizer extends PApplet {

    private FFT fft;
    private AudioIn in;
    private int bands = 16;
    private float[] spectrum = new float[bands];

    public static void main(String[] args) {
        PApplet.main(AudioVisualizer.class.getCanonicalName());
    }

    @Override
    public void settings() {
        size(512, 360);
    }

    @Override
    public void setup() {
        background(255);

        // Create an Input stream which is routed into the Amplitude analyzer
        fft = new FFT(this, bands);
        in = new AudioIn(this);
        // start the Audio Input
        in.start();
        in.play();

        // patch the AudioIn
        fft.input(in);
    }

    @Override
    public void draw() {
        background(255);
        fft.analyze(spectrum);

        for(int i = 0; i < bands; i++){
            // The result of the FFT is normalized
            // draw the line for frequency band i scaling it up by 5 to get more amplitude.
            line( i, height, i, height - spectrum[i]*height*5 );
        }
    }
}