Java 8 throw exception if stream returns no results [duplicate]

Question

I am curious if it's possible to use orElseThrow() in the following situation or if there a more Java 8 way to do the equivalent of this as a 1-liner?

Collection<Foo> foo = blah.stream().filter(somePredicate).collect(Collectors.toList());
if (foo.isEmpty()) {
  throw new Exception("blah");
}

Answer 1

You could try this:

Collection<Foo> foo = blah.stream().filter(somePredicate)
    .collect(Collectors.collectingAndThen(Collectors.toList(), Optional::of))
    .filter(l -> !l.isEmpty())
    .orElseThrow(() -> new Exception("blah"))

Note that comparing to your code this allocates an extra Optional instance.