Java Language Finding the First Element that Matches a Predicate


Example

It is possible to find the first element of a Stream that matches a condition.

For this example, we will find the first Integer whose square is over 50000.

IntStream.iterate(1, i -> i + 1) // Generate an infinite stream 1,2,3,4...
    .filter(i -> (i*i) > 50000) // Filter to find elements where the square is >50000
    .findFirst(); // Find the first filtered element

This expression will return an OptionalInt with the result.

Note that with an infinite Stream, Java will keep checking each element until it finds a result. With a finite Stream, if Java runs out of elements but still can't find a result, it returns an empty OptionalInt.