```java
package main.java.xyz.terrific.mp3_player;

import javazoom.jl.decoder.JavaLayerException;
import javazoom.jl.player.AudioDevice;
import javazoom.jl.player.FactoryRegistry;
import javazoom.jl.player.JavaSoundAudioDevice;
import javazoom.jl.player.advanced.AdvancedPlayer;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MusicPlayer {

    private File mp3_file;
    private final String filename;
    private String filepath;

    private FileInputStream fileInputStream;
    private BufferedInputStream bufferedInputStream;

    Player player;
    private final Thread playThread;
    private final Thread resumeThread;

    private final ExecutorService executor = Executors.newCachedThreadPool();

    private long totalLength;
    private long pause;

    float gain;
    Boolean paused = false;

    public MusicPlayer(String mp3_in, float gain) {
        this(new File(mp3_in), gain);
    }
    public MusicPlayer(String mp3_in) {
        this(new File(mp3_in), 0);
    }
    public MusicPlayer(File mp3_in) {
        this(mp3_in, 0);
    }
    public MusicPlayer(File mp3_in, float gain) {
        mp3_file = mp3_in;
        filename = mp3_file.getName();
        filepath = mp3_file.getAbsolutePath();
        this.gain = gain;

        playThread = new Thread(() -> {
            try {
                fileInputStream = new FileInputStream(mp3_file);
                bufferedInputStream = new BufferedInputStream(fileInputStream);

                player = new Player(bufferedInputStream);
                player.setGain(gain);
                totalLength = fileInputStream.available();
                player.play();
            } catch (IOException | JavaLayerException e) {
                e.printStackTrace();
            }
        });
        resumeThread = new Thread(() -> {
            try {
                fileInputStream = new FileInputStream(mp3_file);
                bufferedInputStream = new BufferedInputStream(fileInputStream);

                player = new Player(bufferedInputStream);
                player.setGain(gain);
                fileInputStream.skip(totalLength - pause);
                player.play();
            } catch (JavaLayerException | IOException e) {
                e.printStackTrace();
            }
        });
    }

    public void play() {
        executor.submit(playThread);
        System.out.println("Now Playing: " + filename.replace(".mp3", ""));
    }

    public void pause() {
        if (paused) {
            paused = false;
            executor.submit(resumeThread);
            System.out.println("Resumed Playing: " + filename.replace(".mp3", ""));
        } else if (player != null) {
            try {
                pause = fileInputStream.available();
                paused = true;
                player.close();
                System.out.println("Paused Playing: " + filename.replace(".mp3", ""));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public void stop() {
        if (player != null) {
            player.close();
            System.out.println("Stopped Playing: " + filename.replace(".mp3", ""));
        }
    }
}
```