Add Duration methods for days, hours, minutes, seconds, etc.

[tprochazka]

Would be great to integrate this to the backport:
https://bugs.openjdk.java.net/browse/JDK-8142936

[jodastephen]

Seems like a good idea. However, for IP reasons, it needs someone other than me to do it (and whoever does it must not look at the source code of OpenJDK - just the Javadoc.

[sschaap]

@jodastephen Had a quick look at this. Noticed your comment on the OpenJDK issue that modulo operator might not be appropriate for negative numbers. Behavior of the java.time implementation seems to match that exactly, though. Thoughts?

Sample code:

package com.example;

import java.time.Duration;

public class Issue76 {
    
    public static void main(String[] args) {
        Duration duration = Duration.ofHours(-1).plusSeconds(-1);
        System.out.printf(
                "Duration [%s] seconds = %dh %ds%n%n",
                duration, duration.toHoursPart(), duration.toSecondsPart());

        System.out.printf("-1 mod 60 = %d%n", (-1 % 60));
        System.out.printf("-1 floorMod 60 = %d%n", Math.floorMod(-1, 60));
    }
}

Output:

Duration [PT-1H-1S] seconds = -1h -1s

-1 mod 60 = -1
-1 floorMod 60 = 59

[jodastephen]

I'd expect PT-1H-1S to return:

• toHoursPart() = -1
• toSecondsPart() = -1

(it is 1 hour and 1 second less than zero)