java drawing 2 (multiple) waveform using AudioWaveformCreator

Question

This question is regarding the code used to answer on this thread. I am using the code posted by Nicholas DiPiazza and later the variant by Andrew Thompson. I am adding a second AudioWaveformCreator to this code and the result is the same for the both of AWC. I cant figure out why. What i am trying to do is to show 2 different waveform (from different file) in a single JOptionpane.

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.font.FontRenderContext;
import java.awt.font.LineBreakMeasurer;
import java.awt.font.TextAttribute;
import java.awt.font.TextLayout;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.text.AttributedCharacterIterator;
import java.text.AttributedString;
import java.util.Vector;

import javax.imageio.ImageIO;
import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.TargetDataLine;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JOptionPane;


public class AudioWaveformCreator2 {
    AudioInputStream audioInputStream;
    Vector<Line2D.Double> lines = new Vector<Line2D.Double>();
    String errStr;
    Capture capture = new Capture();
    double duration, seconds;
    //File file;
    String fileName = "out.png";
    SamplingGraph samplingGraph;
    String waveformFilename;
    Color imageBackgroundColor = new Color(20,20,20);
    Object result = null;

    public AudioWaveformCreator2(File url, String waveformFilename) throws Exception {
        if (url != null) {
            try {
                errStr = null;
                audioInputStream = AudioSystem.getAudioInputStream(url);
                long milliseconds = (long)((audioInputStream.getFrameLength() * 1000) / audioInputStream.getFormat().getFrameRate());
                duration = milliseconds / 1000.0;
                samplingGraph = new SamplingGraph();
                samplingGraph.createWaveForm(null);                
            } catch (Exception ex) { 
                reportStatus(ex.toString());
                throw ex;
            }
        } else {
            reportStatus("Audio file required.");
        }
    }
    /**
     * Render a WaveForm.
     */
    class SamplingGraph implements Runnable {

        private Thread thread;
        private Font font10 = new Font("serif", Font.PLAIN, 10);
        private Font font12 = new Font("serif", Font.PLAIN, 12);
        Color jfcBlue = new Color(000, 000, 255);
        Color pink = new Color(255, 175, 175);


        public SamplingGraph() {
        }


        public void createWaveForm(byte[] audioBytes) {

            lines.removeAllElements();  // clear the old vector

            AudioFormat format = audioInputStream.getFormat();
            if (audioBytes == null) {
                try {
                    audioBytes = new byte[
                        (int) (audioInputStream.getFrameLength() 
                        * format.getFrameSize())];
                    audioInputStream.read(audioBytes);
                } catch (Exception ex) { 
                    reportStatus(ex.getMessage());
                    return; 
                }
            }
            int w = 500;
            int h = 200;
            int[] audioData = null;
            if (format.getSampleSizeInBits() == 16) {
                 int nlengthInSamples = audioBytes.length / 2;
                 audioData = new int[nlengthInSamples];
                 if (format.isBigEndian()) {
                    for (int i = 0; i < nlengthInSamples; i++) {
                         /* First byte is MSB (high order) */
                         int MSB = (int) audioBytes[2*i];
                         /* Second byte is LSB (low order) */
                         int LSB = (int) audioBytes[2*i+1];
                         audioData[i] = MSB << 8 | (255 & LSB);
                     }
                 } else {
                     for (int i = 0; i < nlengthInSamples; i++) {
                         /* First byte is LSB (low order) */
                         int LSB = (int) audioBytes[2*i];
                         /* Second byte is MSB (high order) */
                         int MSB = (int) audioBytes[2*i+1];
                         audioData[i] = MSB << 8 | (255 & LSB);
                     }
                 }
             } else if (format.getSampleSizeInBits() == 8) {
                 int nlengthInSamples = audioBytes.length;
                 audioData = new int[nlengthInSamples];
                 if (format.getEncoding().toString().startsWith("PCM_SIGN")) {
                     for (int i = 0; i < audioBytes.length; i++) {
                         audioData[i] = audioBytes[i];
                     }
                 } else {
                     for (int i = 0; i < audioBytes.length; i++) {
                         audioData[i] = audioBytes[i] - 128;
                     }
                 }
            }

            int frames_per_pixel = audioBytes.length / format.getFrameSize()/w;
            byte my_byte = 0;
            double y_last = 0;
            int numChannels = format.getChannels();
            for (double x = 0; x < w && audioData != null; x++) {
                int idx = (int) (frames_per_pixel * numChannels * x);
                if (format.getSampleSizeInBits() == 8) {
                     my_byte = (byte) audioData[idx];
                } else {
                     my_byte = (byte) (128 * audioData[idx] / 32768 );
                }
                double y_new = (double) (h * (128 - my_byte) / 256);
                lines.add(new Line2D.Double(x, y_last, x, y_new));
                y_last = y_new;
            }
            saveToFile();
        }


        public void saveToFile() {            
            int w = 500;
            int h = 200;
            int INFOPAD = 0;

            BufferedImage bufferedImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
            Graphics2D g2 = bufferedImage.createGraphics();

            createSampleOnGraphicsContext(w, h, INFOPAD, g2);            
            g2.dispose();
            // Write generated image to a file
            try {
                // Save as PNG
                File file = new File(fileName);
                System.out.println(file.getAbsolutePath());
                ImageIO.write(bufferedImage, "png", file);
                result =  new ImageIcon(fileName);
            } catch (IOException e) {
            }
        }


        private void createSampleOnGraphicsContext(int w, int h, int INFOPAD, Graphics2D g2) {            
            g2.setBackground(imageBackgroundColor);
            g2.clearRect(0, 0, w, h);
            g2.setColor(Color.white);
            g2.fillRect(0, h-INFOPAD, w, INFOPAD);

            if (errStr != null) {
                g2.setColor(jfcBlue);
                g2.setFont(new Font("serif", Font.BOLD, 18));
                g2.drawString("ERROR", 5, 20);
                AttributedString as = new AttributedString(errStr);
                as.addAttribute(TextAttribute.FONT, font12, 0, errStr.length());
                AttributedCharacterIterator aci = as.getIterator();
                FontRenderContext frc = g2.getFontRenderContext();
                LineBreakMeasurer lbm = new LineBreakMeasurer(aci, frc);
                float x = 5, y = 25;
                lbm.setPosition(0);
                while (lbm.getPosition() < errStr.length()) {
                    TextLayout tl = lbm.nextLayout(w-x-5);
                    if (!tl.isLeftToRight()) {
                        x = w - tl.getAdvance();
                    }
                    tl.draw(g2, x, y += tl.getAscent());
                    y += tl.getDescent() + tl.getLeading();
                }
            } else if (capture.thread != null) {
                g2.setColor(Color.black);
                g2.setFont(font12);
                //g2.drawString("Length: " + String.valueOf(seconds), 3, h-4);
            } else {
                g2.setColor(Color.black);
                g2.setFont(font12);
                //g2.drawString("File: " + fileName + "  Length: " + String.valueOf(duration) + "  Position: " + String.valueOf(seconds), 3, h-4);

                if (audioInputStream != null) {
                    // .. render sampling graph ..
                    g2.setColor(jfcBlue);
                    for (int i = 1; i < lines.size(); i++) {
                        g2.draw((Line2D) lines.get(i));
                    }

                    // .. draw current position ..
                    if (seconds != 0) {
                        double loc = seconds/duration*w;
                        g2.setColor(pink);
                        g2.setStroke(new BasicStroke(3));
                        g2.draw(new Line2D.Double(loc, 0, loc, h-INFOPAD-2));
                    }
                }
            }
        }

        public void start() {
            thread = new Thread(this);
            thread.setName("SamplingGraph");
            thread.start();
            seconds = 0;
        }

        public void stop() {
            if (thread != null) {
                thread.interrupt();
            }
            thread = null;
        }

        public void run() {
            seconds = 0;
            while (thread != null) {
                if ( (capture.line != null) && (capture.line.isActive()) ) {
                    long milliseconds = (long)(capture.line.getMicrosecondPosition() / 1000);
                    seconds =  milliseconds / 1000.0;
                }
                try { thread.sleep(100); } catch (Exception e) { break; }                              
                while ((capture.line != null && !capture.line.isActive())) 
                {
                    try { thread.sleep(10); } catch (Exception e) { break; }
                }
            }
            seconds = 0;
        }
    } // End class SamplingGraph

    /** 
     * Reads data from the input channel and writes to the output stream
     */
    class Capture implements Runnable {

        TargetDataLine line;
        Thread thread;

        public void start() {
            errStr = null;
            thread = new Thread(this);
            thread.setName("Capture");
            thread.start();
        }

        public void stop() {
            thread = null;
        }

        private void shutDown(String message) {
            if ((errStr = message) != null && thread != null) {
                thread = null;
                samplingGraph.stop();                
                System.err.println(errStr);
            }
        }

        public void run() {

            duration = 0;
            audioInputStream = null;

            // define the required attributes for our line, 
            // and make sure a compatible line is supported.

            AudioFormat format = audioInputStream.getFormat();
            DataLine.Info info = new DataLine.Info(TargetDataLine.class, 
                format);

            if (!AudioSystem.isLineSupported(info)) {
                shutDown("Line matching " + info + " not supported.");
                return;
            }

            // get and open the target data line for capture.

            try {
                line = (TargetDataLine) AudioSystem.getLine(info);
                line.open(format, line.getBufferSize());
            } catch (LineUnavailableException ex) { 
                shutDown("Unable to open the line: " + ex);
                return;
            } catch (SecurityException ex) { 
                shutDown(ex.toString());
                //JavaSound.showInfoDialog();
                return;
            } catch (Exception ex) { 
                shutDown(ex.toString());
                return;
            }

            // play back the captured audio data
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int frameSizeInBytes = format.getFrameSize();
            int bufferLengthInFrames = line.getBufferSize() / 8;
            int bufferLengthInBytes = bufferLengthInFrames * frameSizeInBytes;
            byte[] data = new byte[bufferLengthInBytes];
            int numBytesRead;

            line.start();

            while (thread != null) {
                if((numBytesRead = line.read(data, 0, bufferLengthInBytes)) == -1) {
                    break;
                }
                out.write(data, 0, numBytesRead);
            }

            // we reached the end of the stream.  stop and close the line.
            line.stop();
            line.close();
            line = null;

            // stop and close the output stream
            try {
                out.flush();
                out.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            // load bytes into the audio input stream for playback

            byte audioBytes[] = out.toByteArray();
            ByteArrayInputStream bais = new ByteArrayInputStream(audioBytes);
            audioInputStream = new AudioInputStream(bais, format, audioBytes.length / frameSizeInBytes);

            long milliseconds = (long)((audioInputStream.getFrameLength() * 1000) / format.getFrameRate());
            duration = milliseconds / 1000.0;

            try {
                audioInputStream.reset();
            } catch (Exception ex) { 
                ex.printStackTrace(); 
                return;
            }

            samplingGraph.createWaveForm(audioBytes);
        }
    } // End class Capture    

    public static void main(String [] args) throws Exception {

        AudioWaveformCreator2 awc = new AudioWaveformCreator2(new File("E:/PRODI ILKOM/Semester VIII/TA/wave/cars062.wav"), "cars062.png");
        AudioWaveformCreator2 awc2 = new AudioWaveformCreator2(new File("E:/PRODI ILKOM/Semester VIII/TA/wave/plain wav.wav"), "plain wav.png");
        Object[] fields = {
                "Plain", awc.result
                ,"Stego", awc2.result
        };
        JOptionPane.showConfirmDialog(null, fields, "Wave Form", JOptionPane.PLAIN_MESSAGE);
    }

    private void reportStatus(String msg) {
        if ((errStr = msg) != null) {
            System.out.println(errStr);            
        }
    }

    private static void printUsage() {
        System.out.println("AudioWaveformCreator usage: java AudioWaveformCreator.class [path to audio file for generating the image] [path to save waveform image to]");
    }
}

this is what i get two waveform:

Answer 1

When an AudioWaveformCreator2-instance is created, the SamplingGraph#saveToFile-method is subsequently executed. That method stores the previously generated waveform in the file fileName, where fileName is an AudioWaveformCreator2-field initialized with the fixed name out.png. Thus, when more than one AudioWaveformCreator2-instance is created, both instances store their data in the same file out.png and the second file overwrites the first one. After the AudioWaveformCreator2-instance has stored the file, a new ImageIcon is created using the ImageIcon(String filename)-constructor. The source code of ImageIcon (e.g. http://hg.openjdk.java.net/jdk10/jdk10/jdk/file/777356696811/src/java.desktop/share/classes/javax/swing/ImageIcon.java) shows that the ImageIcon(String filename)-constructor calls sometime later the Toolkit.getDefaultToolkit().getImage(filename)-method. The description of that method reveals that there is a kind of caching mechanism to return the same image for requests with the same filename (see e.g. https://docs.oracle.com/javase/10/docs/api/java/awt/Toolkit.html#getImage(java.lang.String)):

Returns an image which gets pixel data from the specified file, whose format can be either GIF, JPEG or PNG. The underlying toolkit attempts to resolve multiple requests with the same filename to the same returned Image. Since the mechanism required to facilitate this sharing of Image objects may continue to hold onto images that are no longer in use for an indefinite period of time, developers are encouraged to implement their own caching of images by using the createImage variant wherever available. If the image data contained in the specified file changes, the Image object returned from this method may still contain stale information which was loaded from the file after a prior call. Previously loaded image data can be manually discarded by calling the flush method on the returned Image.

The caching in combination with the fixed name out.png is responsible for the observed behavior: Although the second AudioWaveformCreator2-instance overwrites the out.png-file the caching mechanism provides the first image and thus, the first image is displayed twice:

A possible solution is the passing and initialization of the file name in the AudioWaveformCreator2-constructor:

public AudioWaveformCreator2(File url, String waveformFilename, String fileName) throws Exception {
    if (url != null) {
        try {
            this.fileName = fileName;
    ...

and

AudioWaveformCreator2 awc = new AudioWaveformCreator2(new File("E:/PRODI ILKOM/Semester VIII/TA/wave/cars062.wav"), "cars062.png", "out.png");
AudioWaveformCreator2 awc2 = new AudioWaveformCreator2(new File("E:/PRODI ILKOM/Semester VIII/TA/wave/plain wav.wav"), "plain wav.png", "out2.png");
...

where the first AudioWaveformCreator2-instance stores the image in the file out.png and the second AudioWaveformCreator2-instance in the file out2.png. Then, the caching mechanism can distinguish both images:

There are other solutions where storing in the same file out.png can remain (i.e. the modification of the AudioWaveformCreator2-constructor isn't necessary), e.g. the usage of the Toolkit.getDefaultToolkit().createImage(filename)-method which is described as follows (see e.g. https://docs.oracle.com/javase/10/docs/api/java/awt/Toolkit.html#createImage(java.lang.String)):

Returns an image which gets pixel data from the specified URL. The returned Image is a new object which will not be shared with any other caller of this method or its getImage variant.

Thus, no caching mechanism is involved and the fix is simply the replacement of

result = new ImageIcon(fileName);

with

result = new ImageIcon(Toolkit.getDefaultToolkit().createImage(fileName));

A third solution which also avoids the caching mechanism is the replacement of

result = new ImageIcon(fileName);

with

result =  new ImageIcon(bufferedImage);

since the ImageIcon(Image image)-constructor doesn't use the Toolkit.getDefaultToolkit().getImage(filename)-method, but directly the data contained in bufferedImage.