How to cast from InputStream to AudioInputStream

Question

Is it possible to cast from an InputStream to an AudioInputStream?

I want to play little sound files at certain events, so I made following SoundThread

import java.io.*;
import javax.sound.sampled.*;

public class SoundThread implements Runnable{

    private String filename;

    SoundThread(String filename) {
        this.filename = filename;
    }

    public void run() {
        try {
            InputStream in = ClassLoader.getSystemResourceAsStream("sounds/"+filename+".wav");
            Clip clip = AudioSystem.getClip();
            clip.open((AudioInputStream)in);
            clip.start();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (NullPointerException e) {
            e.printStackTrace();
        } catch (LineUnavailableException e){
            e.printStackTrace();
        } 
    }
}

I run it with

new Thread(new SoundThread("nameOfTheSoundFile")).start();

At the beginning I handled it with the sun.audio.AudioPlayer and sun.audio.AudioStream, but as soon I put that code in eclipse, it showed me errors. So I tried

AudioInputStream in = (AudioInputStream)ClassLoader.getSystemResourceAsStream("sounds/"+filename+".wav");

to cast the InputStream to AudioInputStream (eclipse didn't show any errors), but running it it throws an ClassCastException. Is there any solution for this problem?

Andrew Thompson · Accepted Answer · 2012-05-15T00:05:20.403

7

Use the AudioSystem to get an AudioInputStream directly from the URL to the resource.

URL url = ClassLoader.getResource("/sounds/"+filename+".wav");
AudioInputStream ais = AudioSystem.getAudioInputStream(url);
Clip clip = AudioSystem.getClip();
clip.open(ais);

See also AudioSystem.getAudioInputStream(InputStream) but this is 'more dangerous'. Java Sound will typically require a repositionable input stream. For some reason that I am not quite clear on, the Class.getResourceAsStream() variants sometimes return a non-repositionable stream.

edited May 15 '12 at 00:05

answered May 14 '12 at 22:34

Andrew Thompson

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1

@Stephen C I tried both ways, once with the code snipped above via URL, the other with AudioSystem.getAudioInputStream(ClassLoader.getSystemResourceAsStream("sounds/"+filename+".wav")). In both ways the code goes through, but no sound is played. I also tried it to start it from cmd (where the original code without class loader worked), but also there was no sound. But especially with the second one I don't understand it: it's exactly the same way like in the original code, except that I don't create the AudioInputStream directly, but via ClassLoader and .getAudioInputStream(InputStream) – Valentino Ru May 14 '12 at 23:18
OK - take a step back & try the exact code shown on the [Java Sound info. page](http://stackoverflow.com/tags/javasound/info) - the 'LoopSound` source. 1) Does that code work for the original looped WAV at my site? 2) Does that code work if you change the URL to point to your WAV? 3) If not, what output does it produce? – Andrew Thompson May 15 '12 at 00:09
Number 1) works fine from eclipse. Number 2) also, but since where in a static method I can't make 'getClass().getResource("/sounds/"check.wav")', I had to change it in URL 'url = LoopSound.class.getResource("/sounds/check.wav")'; When I copy now the exact code in my class SoundThread, the sound isn't plaid. The main difference is that in your code we use an 'invokeLater()' method, while in my code the whole class is extended as runnable. What influence has this? – Valentino Ru May 15 '12 at 09:26
this is now the solution that works. Thank you very much edit: I postes some code here, but it looks very awful. I just don't implement the class with runnable and make a `SwingUtilities.invokeLater()` (Which is empty), and everything is fine – Valentino Ru May 15 '12 at 09:51

Stephen C · Answer 2 · 2012-05-14T23:07:15.163

You can't cast it. In Java, a type cast on a reference type only works if the real object you are casting is already an instance of the target type. For example:

    String myString = new String("42");
    Object obj = (Object) myString;  // OK
    String mystery = (String) obj;   // OK
    String mystery2 = (Integer) obj; // FAIL

The first two succeed because the string object that we created in the first line is an instance of Object (because String is a subtype of Object), and an instance of String. The third one fails because a String is NOT an Integer.

In your example, the object that you get from getSystemResourceAsStream is a raw stream containing (presumably) audio data. It is not an audio stream; i.e. not an instance of AudioInputStream.

You have to wrap the raw input stream, something like this:

    InputStream in = ClassLoader.getSystemResourceAsStream(
        "sounds/"+filename+".wav");
    AudioFormat format = ...
    int length = ...
    AudioInputStream audio = new AudioInputStream(in, format, length);

or use one of AudioSystem.getAudioInputStream(...) factory methods, which does the wrapping under the hood.

See Andrew Thomson's answer for details of the RIGHT way to do this.

@Andrew Thompson I just saw your editings of your posts after posting my comment. I want to try your edited solution with the AudioFormat and the length, but even with reading the API I don't really understand where I find out the parameters to create the AudioFormat respectively the length. I suppose (because we haven't created a "sound file" yet), there are no .getSampleBitRate()-methods that I could use, am I right? How do I get the right parameters? — Valentino Ru, May 14 '12 at 23:27
@ValentinoRu - I >>recommend<< you do it the Andrew Thomson's way. If you want to do it explicitly (using the constructor), take a look at the code of the `getAudioInputStream` method(s) to figure out how to form the parameters that are required. — Stephen C, May 15 '12 at 00:33
@ValentinoRu - the real point of my Answer is to explain how casting works in Java, and (therefore) why you can't solve this by casting. — Stephen C, May 15 '12 at 00:35

score 0 · Answer 3 · answered May 14 '12 at 22:33

0

The InputStream returned by getSystemResourceAsStream is not an AudioInputStream, so casting it will never work. Just create a new AudioInputStream instead.

answered May 14 '12 at 22:33

Jeffrey

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How to cast from InputStream to AudioInputStream

3 Answers3

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