How to match stream elements but return false if non exists?

Question

I have a stream and would like to check if all match a filter. If all match, return true.

But, if the stream is empty, I\'d like to return false

Answer 1

If you are OK with losing your characteristics and parallelism, this for example:

 public static boolean validate(Stream stream) {
    Iterator it = stream.iterator();

    if (!it.hasNext()) {
        return false;
    }

    return StreamSupport.stream(Spliterators.spliteratorUnknownSize(it, 0), false)
            .peek(System.out::println)
            .allMatch(x -> x.contains("a"));

}