Cannot play embedded sound in a jar file

Question

I am creating a software for personal use titled BatteryBeeper. It will remind me to charge the laptop when the charge is whatever I set to be reminded at.

It is supposed to play a sound when the charge hits the set threshold.

I had a look at the answer: sound not playing in jar and my AudioInputStream is constructed similar to what Jigar Joshi mentioned.

However I get a null exception:

java.lang.NullPointerException
    at com.sun.media.sound.SoftMidiAudioFileReader.getAudioInputStream(Unknown Source)
    at javax.sound.sampled.AudioSystem.getAudioInputStream(Unknown Source)
    at demo.BatteryBeeper.setupSoundPlayback(BatteryBeeper.java:169)
    at demo.BatteryBeeper.<init>(BatteryBeeper.java:41)
    at demo.BatteryBeeper.main(BatteryBeeper.java:35)  

Here is my code to load the sound:

public void setupSoundPlayback(){
        try{
            buzzer = AudioSystem.getClip();
            in = AudioSystem.getAudioInputStream(BatteryBeeper.class.
                    getResourceAsStream("sound/buzzer3_x.wav"));
            buzzer.open(in);
        }catch(Exception e){
            e.printStackTrace();
        }

    }  

Here is the code to play it:

public void playSound(){
        buzzer.start();
    }  

What is causing the problem ?

Misc

This is a usual Eclipse project. There is a sound folder under src which has the wave file

Edit

After AlexR's answer, I changed the path and got a new exception:

javax.sound.sampled.UnsupportedAudioFileException: could not get audio input stream from input stream
    at javax.sound.sampled.AudioSystem.getAudioInputStream(Unknown Source)
    at demo.BatteryBeeper.setupSoundPlayback(BatteryBeeper.java:169)
    at demo.BatteryBeeper.<init>(BatteryBeeper.java:41)
    at demo.BatteryBeeper.main(BatteryBeeper.java:35)

Answer 1

You problem is not in playing the sound. Your problem is in access to embedded resource. When you are using BatteryBeeper.class.getResourceAsStream("sound/buzzer3_x.wav") you try to retrieve resource located in same package where class BatteryBeeper is. This means that your file is in /demo/sound/buzzer3_x.wav. It seems this is wrong. If your file really is in sound/buzzer3_x.wav use getResourceAsStream("/sound/buzzer3_x.wav") (pay attention on the leading slash in the path).