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I'm trying to control the volume of a file with keyinput. But all I get is a null error:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "javax.sound.sampled.FloatControl.setValue(float)" because "this.fc" is null

I tried to set it to value cVol but I also get an error, so I think the error is somewhere different.

Here's my sound file. I want to change the volume with the 3 methods below. I used a debug text and the program arrived in the method. So the error is somewhere else. But I can't find it!

public class Sound {
    
    Clip clip;
    URL soundURL[] = new URL[30];
    float prevVol = 0;
    float cVol = 6.0f;
    boolean mute = false;
    FloatControl fc;
    
    public Sound() {
        
        soundURL[0] = getClass().getResource("/sound/BlueBoyAdventure.wav");
        soundURL[1] = getClass().getResource("/sound/coin.wav");

    }
    
    public void setFile(int i) {
        
        try {
            
            AudioInputStream ais = AudioSystem.getAudioInputStream(soundURL[i]);
            clip = AudioSystem.getClip();
            clip.open(ais);
            fc = (FloatControl) clip.getControl(FloatControl.Type.MASTER_GAIN);
            fc.setValue(cVol);
            
            
        }catch (Exception e) {
            
        }
    }
    public void volUp() {
        cVol += 1.0f;
        System.out.println("up");
        if(cVol > 6.0f) {
            cVol = 6.0f;
        }
        fc.setValue(cVol);
    }
    public void volDown() {
        cVol -= 1.0f;
        if(cVol > -80.0f) {
            cVol = -80.0f;
        }
        fc.setValue(cVol);  
    }
    public void mute() {
        if(mute == false) {
            prevVol = cVol;
            cVol = -80.0f;
            fc.setValue(cVol);
            mute = true;
        }else if(mute == true) {
            cVol = prevVol;
            fc.setValue(cVol);
            mute = false;
            
        }
    }
    
}

My keyHander. I want to control the volume with 0,9,8:

    if(code == KeyEvent.VK_8) {
            s.volUp();
            gp.ui.addMsg("volume up");
        }
        if(code == KeyEvent.VK_9) {
            s.volDown();
            gp.ui.addMsg("volume down");
        }
        if(code == KeyEvent.VK_0) {
            s.mute();
            gp.ui.addMsg("volume muted");
        }
```
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  • \$\begingroup\$ What this tells you is either that your setFile function has not run to completion to initialize fc, or that that clip has no FloatControl of type MASTER_GAIN, so getControl() is returning null. I'm not sure why that would be the case, but since you seem to be loading it from a file, one speculative possibility is that the clip hasn't finished loading yet. \$\endgroup\$ Commented Mar 18, 2022 at 16:38
  • \$\begingroup\$ @DMGregory I don't think so the files aren't big and normally it works(without the volume stuff). But if that's the case, what would you recommend doing? \$\endgroup\$ Commented Mar 18, 2022 at 16:52
  • 2
    \$\begingroup\$ Have you checked whether an exception is being thrown in that empty catch block? This could be masking the root issue. \$\endgroup\$ Commented Mar 19, 2022 at 12:21
  • \$\begingroup\$ Agree about the empty catch block - while at times convenient, an empty catch can allow code to continue past what should have been a terminal error leaving the program in an unreliable state. If you add a breakpoint & step through the code, you can examine the state of clip & fc to see if they are initializing properly. \$\endgroup\$ Commented Mar 21, 2022 at 13:54

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