public class AudioRecorder implements Runnable {

    private static final int SAMPLERATE = 8000;
    private static final int BUFFERSIZE = SAMPLERATE*2;
   
    private TargetDataLine tdl;
    private FileOutputStream fileOutputStream;

    AudioRecorder(final TargetDataLine tdl, final FileOutputStream fileOutputStream) {
        this.tdl = tdl;
        this.fileOutputStream = fileOutputStream;
    }

    @Override
    public void run() {
        byte[] abBuffer = new byte[BUFFERSIZE];

        ByteArrayOutputStream baos = new ByteArrayOutputStream(); // this will store sound data

        tdl.start();

        try {
            while (!Thread.interrupted()) {
                // waiting for the buffer to get filled
                while (tdl.available() < tdl.getBufferSize() * 0.5)
                    Thread.sleep(0, 1); // without this, the audio will be choppy
   
                int bytesRead = tdl.read(abBuffer, 0, tdl.available());
                baos.write(abBuffer, 0, bytesRead);
                System.out.println("Captured " + bytesRead + " bytes.");
            }
        } catch (InterruptedException e) {
        }

        tdl.stop();
        tdl.close();

        // now writing the stored data into a .wav format file
        byte[] abData = baos.toByteArray();
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(abData);

        AudioInputStream audioInputStream = new AudioInputStream(byteArrayInputStream, tdl.getFormat(), abData.length / tdl.getFormat().getFrameSize());
        try {
            AudioSystem.write(audioInputStream, AudioFileFormat.Type.WAVE, fileOutputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            audioInputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        AudioFormat audioFormat = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED, SAMPLERATE, 16, 1, 2, SAMPLERATE, false);
        DataLine.Info info = new DataLine.Info(TargetDataLine.class, audioFormat, BUFFERSIZE);

        TargetDataLine targetDataLine = null;
        try {
            targetDataLine = (TargetDataLine) AudioSystem.getLine(info);
            targetDataLine.open(audioFormat, BUFFERSIZE);
            System.out.println("Buffer size: " + targetDataLine.getBufferSize());
        } catch (LineUnavailableException e1) {
            e1.printStackTrace();
        }

        FileOutputStream outputStream = null;
        try {
            outputStream = new FileOutputStream("output.wav");
        } catch (FileNotFoundException e1) {
            e1.printStackTrace();
        }

        // creating the recorder thread from this class' instance
        AudioRecorder audioRecorderDirect = new AudioRecorder(targetDataLine, outputStream);
        Thread audioRecorderThread = new Thread(audioRecorderDirect);

        // we use this to read line from the standard input
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Press ENTER to start recording!");
        try {
            br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }

        audioRecorderThread.setPriority(Thread.MAX_PRIORITY);
        audioRecorderThread.start();

        System.out.println("Recording... press ENTER to stop recording!");
        try {
            br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }

        audioRecorderThread.interrupt();

        try {
            // waiting for the recorder thread to stop
            audioRecorderThread.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Recording stopped.");
    }
}