What is the best way to generate a unique and short file name in Java

Question

I don\'t necessarily want to use UUIDs since they are fairly long.

The file just needs to be unique within its directory.

One thought which comes to mind is

Answer 1

This works for me:

String generateUniqueFileName() {
    String filename = "";
    long millis = System.currentTimeMillis();
    String datetime = new Date().toGMTString();
    datetime = datetime.replace(" ", "");
    datetime = datetime.replace(":", "");
    String rndchars = RandomStringUtils.randomAlphanumeric(16);
    filename = rndchars + "_" + datetime + "_" + millis;
    return filename;
}

// USE:

String newFile;
do{
newFile=generateUniqueFileName() + "." + FileExt;
}
while(new File(basePath+newFile).exists());

Output filenames should look like :

2OoBwH8OwYGKW2QE_4Sep2013061732GMT_1378275452253.Ext