Concatenate WAV files in Java

public Boolean concatenateFiles(List<String> sourceFilesList, String destinationFileName) throws Exception {
    Boolean result = false;

    AudioInputStream audioInputStream = null;
    List<AudioInputStream> audioInputStreamList = null;
    AudioFormat audioFormat = null;
    Long frameLength = null;

    try {
        // loop through our files first and load them up
        for (String sourceFile : sourceFilesList) {
            audioInputStream = AudioSystem.getAudioInputStream(new File(sourceFile));

            // get the format of first file
            if (audioFormat == null) {
                audioFormat = audioInputStream.getFormat();
            }

            // add it to our stream list
            if (audioInputStreamList == null) {
                audioInputStreamList = new ArrayList<AudioInputStream>();
            }
            audioInputStreamList.add(audioInputStream);

            // keep calculating frame length
            if(frameLength == null) {
                frameLength = audioInputStream.getFrameLength();
            } else {
                frameLength += audioInputStream.getFrameLength();
            }
        }

        // now write our concatenated file
        AudioSystem.write(new AudioInputStream(new SequenceInputStream(Collections.enumeration(audioInputStreamList)), audioFormat, frameLength), Type.WAVE, new File(destinationFileName));

        // if all is good, return true
        result = true;
    } finally {
        if (audioInputStream != null) {
            audioInputStream.close();
        }
        if (audioInputStreamList != null) {
            audioInputStreamList = null;
        }
    }

    return result;
}