Invariably?

I have a list of strings (tagList) that needs to be shared between multiple threads for reading, so I create an immutable version of this file and pass it to streams, im not sure if it is thread safe, as streams only read this list so I think should this be good?

also, when I pass this unmodifialble list to streams, does it transfer one copy and share streams or create multiple copies and transfer one copy to each stream?

here is my code:

final List<String> tList = Collections.unmodifiableList(tagList);
List<Future<Void>> calls = new ArrayList<Future<Void>>();

FileStatus[] fsta = _fileSystem.listStatus(p);      
for (FileStatus sta : fsta) {
    final Path path = new Path(sta.getPath(), "data.txt");
    if (!_fileSystem.exists(path)) {        
        continue;
    }
    else {
        calls.add(_exec.submit(new Callable<Void>() {
            @Override
            public Void call() throws Exception {
                filterData(path, tList);
                return null;
            }
        }));
    }
}