音频出现Java错误，试图播放声音

Question

我正在使用一本旧书（2005年）中的代码，因此我怀疑问题是由于此而引起的。我正在阅读一章，该章解释了如何播放声音，并且正在将代码从书中复制到Eclipse，但是它使我充满了错误。问题似乎始于此行：

g.drawString（“” + sample.getFormat（）。toString（），10，15 * y ++）;

这是完整的代码：

import java.awt.*;
import java.applet.*;
import java.io.*;
import java.net.*;
import javax.sound.sampled.*;

public class PlaySound extends Applet {
    String filename = "thrust.wav";
    AudioInputStream sample;
    
    private URL getURL(String filename) {
        URL url = null;
        try {
            url = this.getClass().getResource(filename);
        }
        catch (Exception e) {}
        return url;
    }
    
    public void init() {
        try {
            sample = AudioSystem.getAudioInputStream(getURL(filename));
            // create a sound buffer
            Clip clip = AudioSystem.getClip();
            // load the audio file
            clip.open(sample);
            // play the sound clip
            clip.start();
        }
        catch (MalformedURLException e) {
        } catch (IOException e) {
        } catch (LineUnavailableException e) {
        } catch (UnsupportedAudioFileException e) {
        } catch (Exception e) {}
    }
    
    // the paint event handles the screen refresh
    public void paint(Graphics g) {
        int y = 1;
        g.drawString("Sample file: " + filename, 10, 15*y++);
        g.drawString(" " + sample.getFormat().toString(), 10, 15*y++);
        g.drawString("  Sampling rate: " + (int)sample.getFormat().getSampleRate(), 10, 15*y++);
        g.drawString("  Sample channels: " + sample.getFormat().getChannels(), 10, 15*y++);
        g.drawString("  Encoded format: " + sample.getFormat().getEncoding().toString(), 10, 15*y++);
        g.drawString("  Sample size: " + sample.getFormat().getSampleSizeInBits() + "-bit", 10, 15*y++);
        g.drawString(" Frame size: " + sample.getFormat().getFrameSize(), 10, 15*y++);
    }
}

在这里编辑是错误：

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
    at PlaySound.paint(PlaySound.java:41)
    at sun.awt.RepaintArea.paintComponent(Unknown Source)
    at sun.awt.RepaintArea.paint(Unknown Source)
    at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
    at PlaySound.paint(PlaySound.java:41)
    at sun.awt.RepaintArea.paintComponent(Unknown Source)
    at sun.awt.RepaintArea.paint(Unknown Source)
    at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)