How to get minimum LocalDateTime from array in Java

Question

I have an array:

LocalDateTime[] onTimes

I would like to find an efficient way (without iteration) of finding the minimum LocalDateTime.

Is there a quick way to do this?

Answer 1

You could, conceivably, use recursion; but I would not recommend that for performance. The best way I can think of is using the streams api like

LocalDateTime min = Arrays.stream(onTimes).min(Comparator.naturalOrder())
        .orElseThrow();

Note: This still iterates all elements internally to find the minimum.

For completeness sake; to do this without iteration, as I said, might be done recursively.

public static LocalDateTime getMinimum(LocalDateTime[] onTimes) {
    return getMinimum(onTimes, 0);
}

private static LocalDateTime getMinimum(LocalDateTime[] onTimes, int i) {
    if (i + 1 < onTimes.length) {
        return min(onTimes[i], getMinimum(onTimes, i + 1));
    } else {
        return onTimes[i];
    }
}

private static LocalDateTime min(LocalDateTime a, LocalDateTime b) {
    if (a.compareTo(b) <= 0) {
        return a;
    }
    return b;
}