public class AudioRecorder implements Runnable {

    // note that this is declared as static so if we stop/close it, the thread will stop
    private static TargetDataLine tdl;
    private File outputFile;

    AudioRecorder(final TargetDataLine tdl, final File outputFile) {
        AudioRecorder.tdl = tdl;
        this.outputFile = outputFile;
    }

    @Override
    public void run() {
        tdl.start();
        try {
            // this will block until tdl doesn't get closed
            AudioSystem.write(new AudioInputStream(tdl), AudioFileFormat.Type.WAVE, outputFile);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void stopRecording() {
        tdl.stop();
        tdl.close();
    }
   
    public static void main(String[] args) {
        File outputFile = new File("output.wav");

        AudioFormat audioFormat = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED, 44100.0F, 16, 2, 4, 44100.0F, false);
        DataLine.Info info = new DataLine.Info(TargetDataLine.class, audioFormat);

        TargetDataLine targetDataLine = null;
        try {
            targetDataLine = (TargetDataLine) AudioSystem.getLine(info);
            targetDataLine.open(audioFormat);
        } catch (LineUnavailableException e1) {
            e1.printStackTrace();
        }

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

        // 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.start();

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

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