Recording speakers Ouput using Java

Question

I want to ask the repetitive question of how to record the audio send to the speakers. But I want some insights to the previously answered.

I went to this page: Capturing speaker output in Java

I saw this code posted by a developer:

import javax.sound.sampled.*;
import java.io.*;

public class JavaSoundRecorder {
    // record duration, in milliseconds
    static final long RECORD_TIME = 10000;  // 1 minute

// path of the wav file
File wavFile = new File("E:/RecordAudio.wav");

// format of audio file
AudioFileFormat.Type fileType = AudioFileFormat.Type.WAVE;

// the line from which audio data is captured
TargetDataLine line;

/**
 * Defines an audio format
 */
AudioFormat getAudioFormat() {
    float sampleRate = 16000;
    int sampleSizeInBits = 8;
    int channels = 1;
    boolean signed = true;
    boolean bigEndian = true;
    AudioFormat format = new AudioFormat(sampleRate, sampleSizeInBits,
                                         channels, signed, bigEndian);
    return format;
}

/**
 * Captures the sound and record into a WAV file
 */
void start() {
    try {
        AudioFormat format = getAudioFormat();
        DataLine.Info info = new DataLine.Info(TargetDataLine.class, format);

        // checks if system supports the data line
        if (!AudioSystem.isLineSupported(info)) {
            System.out.println("Line not supported");
            System.exit(0);
        }
        line = (TargetDataLine) AudioSystem.getLine(info);
        line.open(format);
        line.start();   // start capturing

        System.out.println("Start capturing...");

        AudioInputStream ais = new AudioInputStream(line);

        System.out.println("Start recording...");

        // start recording
        AudioSystem.write(ais, fileType, wavFile);

    } catch (LineUnavailableException ex) {
        ex.printStackTrace();
    } catch (IOException ioe) {
        ioe.printStackTrace();
    }
}

/**
 * Closes the target data line to finish capturing and recording
 */
void finish() {
    line.stop();
    line.close();
    System.out.println("Finished");
}

/**
 * Entry to run the program
 */
public static void main(String[] args) {
    final JavaSoundRecorder recorder = new JavaSoundRecorder();

    // creates a new thread that waits for a specified
    // of time before stopping
    Thread stopper = new Thread(new Runnable() {
        public void run() {
            try {
                Thread.sleep(RECORD_TIME);
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            }
            recorder.finish();
        }
    });

    stopper.start();

    // start recording
    recorder.start();
}
}

Now I have some questions I want to ask.

1. This code runs OK on my windows OS but it doesn't work on my Ubuntu on the same machine(dual boot). In Ubuntu it records silence and I tried to get all mixers but can't get it working

2. I want to get the output going to the speakers and I am getting the output of the speakers. The sound of the vicinity with a very little sound of what I actually want.

Please answer my queries of the above 2 questions.

What I want? I want the clear audio that is currently being played and fetched to the speakers of my laptop. I don't want the audio that is already emitted and then re-recorded because that is bad. Also I need a reason as of why my Ubuntu is not supporting this code.(This is vague info but I am using BlueJ in windows to run this and NetBeans on Ubuntu(without sudo)).

I saw some YouTube videos to understand the theory:

1. https://www.youtube.com/watch?v=GVtl19L9GxU
2. https://www.youtube.com/watch?v=PTs01qr9RlY

I read 1 and a half page documentation of oracle here: https://docs.oracle.com/javase/tutorial/sound/accessing.html

There was this thing mentioned in the docs:

An applet running with the applet security manager can play, but not record, audio.
An application running with no security manager can both play and record audio.
An application running with the default security manager can play, but not record, audio.

But I don't think I turned any security manager.

In the end I found no success in what I want to do. Instead of going further in the documentation I thought to ask the question here.