有人能解释为什么这会发生在python列表中

Question

有人能解释一下它的python功能还是什么？

package com.zetcode;

import java.io.IOException;
import java.net.URL;
import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.LineEvent;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.JOptionPane;

public enum SoundEffect {

    EXPLODE("resources/explosion.wav"),
    HITGROUND("resources/impact.wav"),
    CANNON("resources/cannon.wav");

    private Clip clip;

    SoundEffect(String soundFileName) {
        try {
            URL url = this.getClass().getClassLoader().getResource(soundFileName);

            try (AudioInputStream audioInputStream = AudioSystem.getAudioInputStream(url)) {
                clip = AudioSystem.getClip();
                clip.open(audioInputStream);
            }
        } catch (UnsupportedAudioFileException | IOException | LineUnavailableException e) {
            JOptionPane.showMessageDialog(null, "Cannot play sound", "Error",
                    JOptionPane.ERROR_MESSAGE);
        }
    }

    public void play() {

        if (clip.isRunning()) {
            clip.stop();
        }
        clip.setFramePosition(0);
        clip.start();
    }

    static void init() {
        values();
    }    
}

为什么列出'new'包含空元素？