Java8 Streams findFirst and findAny Examples

findFirst() and findAny() are methods in the Stream interface in Java that are used to find the first or any element in a stream that matches a given condition.

Java8 Streams FindFirst

findFirst() returns an Optional object, which contains the first element in the stream that matches the given condition. If no elements match the condition, an empty Optional is returned.

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8);
Optional<Integer> firstEvenNumber = numbers.stream()
    .filter(n -> n % 2 == 0)
    .findFirst();

Java8 Streams FindAny

findAny() also returns an Optional object, which contains any element in the stream that matches the given condition. If no elements match the condition, an empty Optional is returned.

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8);
Optional<Integer> anyEvenNumber = numbers.stream()
    .filter(n -> n % 2 == 0)
    .findAny();

It’s important to note that both findFirst() and findAny() are short-circuiting operations, meaning that they will stop processing the stream as soon as they find the first or any element that matches the given condition. So, the time complexity of both methods is O(1) on average, and O(n) in the worst case.

Also, using findFirst() or findAny() on a parallel stream will return the first or any element encountered in an unspecified order, but using them on a sequential stream will return the first or any element in the encounter order.