Convert arraylist elements order in sequence based on day

Question

Below is the output from database. These sequence orders can not be the same every time. Here the days are not in sequence order . I need these days in sequence order.

ArrayList dayList= [ MONDAY   : 9:00AM - 5:00PM , TUESDAY  : 9:00AM - 5:00PM , WEDNESDAY: 9:00AM - 5:00PM , FRIDAY   : 9:00AM - 5:00PM,  THURSDAY : 9:00AM - 5:00PM , SATURDAY : C L O S E D  , SUNDAY   : C L O S E D , APPOINTMENT REQUIREMENT]

I need to convert the output in sequence order like the below:

[ MONDAY   : 9:00AM - 5:00PM , TUESDAY  : 9:00AM - 5:00PM , WEDNESDAY: 9:00AM - 5:00PM , THURSDAY : 9:00AM - 5:00PM , FRIDAY   : 9:00AM - 5:00PM,  SATURDAY : C L O S E D  , SUNDAY   : C L O S E D , APPOINTMENT REQUIREMENT]

`dayList` looks like `String` representation of the `List`. Could you provide how it looks like using objects? What kind of types do you have? Also, much better is ordering these items on `DB` side. — Michał Ziober, Jan 05 '19 at 00:26
The you need to parse those strings first, so you know the day. What have you tried? — Andreas, Jan 05 '19 at 00:42
It's probably down-voted because there is *literally* NO attempt from OP to solve the issue. — Nicholas K, Jan 05 '19 at 06:14

Andreas · Answer 1 · 2019-01-05T20:26:52.847

Something like this might work. It uses regex to extract the day name, and DayOfWeek from the Java 8 Time API to get the day number from the day name.

List<String> dayList = new ArrayList<>(Arrays.asList(
        "SATURDAY : C L O S E D",
        "TUESDAY  : 9:00AM - 5:00PM",
        "FRIDAY   : 9:00AM - 5:00PM",
        "MONDAY   : 9:00AM - 5:00PM",
        "SUNDAY   : C L O S E D",
        "WEDNESDAY: 9:00AM - 5:00PM",
        "APPOINTMENT REQUIREMENT",
        "THURSDAY : 9:00AM - 5:00PM"));

// Sort list by day name
Pattern p = Pattern.compile("^(\\w+DAY)\\s*:");
dayList.sort(Comparator.<String>comparingInt(s -> {
    Matcher m = p.matcher(s);
    return (m.find() ? DayOfWeek.valueOf(m.group(1)).getValue() : 8);
}));

// Print the sorted list
dayList.forEach(System.out::println);

Output

MONDAY   : 9:00AM - 5:00PM
TUESDAY  : 9:00AM - 5:00PM
WEDNESDAY: 9:00AM - 5:00PM
THURSDAY : 9:00AM - 5:00PM
FRIDAY   : 9:00AM - 5:00PM
SATURDAY : C L O S E D
SUNDAY   : C L O S E D
APPOINTMENT REQUIREMENT

UPDATE Java 5+ solution, same output as above:

final class DayComparator implements Comparator<String> {
    private final Pattern p = Pattern.compile(
            "^(?:(MON)|(TUES)|(WEDNES)|(THURS)|(FRI)|(SATUR)|(SUN))DAY\\s*:");
    public int compare(String s1, String s2) {
        return dayValue(s1) - dayValue(s2);
    }
    private int dayValue(String s) {
        Matcher m = this.p.matcher(s);
        if (m.find())
            for (int i = 1; ; i++)
                if (m.start(i) != -1)
                    return i;
        return 8;
    }
}

List<String> dayList = new ArrayList<String>(Arrays.asList(
        "SATURDAY : C L O S E D",
        "TUESDAY  : 9:00AM - 5:00PM",
        "FRIDAY   : 9:00AM - 5:00PM",
        "MONDAY   : 9:00AM - 5:00PM",
        "SUNDAY   : C L O S E D",
        "WEDNESDAY: 9:00AM - 5:00PM",
        "APPOINTMENT REQUIREMENT",
        "THURSDAY : 9:00AM - 5:00PM"));

// Sort list by day name
Collections.sort(dayList, new DayComparator());

// Print the sorted list
for (String s : dayList)
    System.out.println(s);

Great answer, I can't come up with better but the tag says java-6, perhaps edit? — Robert Bain, Jan 05 '19 at 01:16
For Java 6 & 7, most of the *java.time* functionality is available in the *ThreeTen-Backport* project. — Basil Bourque, Jan 05 '19 at 03:37
@Ravikanth *Huh?!?* I just added code which works for Java 5+ (which means for Java 5 and any later version, which includes Java 5, 6, 7, 8, 9, 10, 11, 12, ...). — Andreas, Jan 06 '19 at 06:07

score 0 · Answer 2 · answered Jan 05 '19 at 21:36

This won't work in Java 6 but the concept holds and is easy enough to translate:

Java 8 streams alternative:

private static final List<String> DATES =
        List.of("MONDAY   : 9:00AM - 5:00PM",
                "TUESDAY  : 9:00AM - 5:00PM",
                "WEDNESDAY: 9:00AM - 5:00PM",
                "FRIDAY   : 9:00AM - 5:00PM",
                "THURSDAY : 9:00AM - 5:00PM",
                "SATURDAY : C L O S E D ",
                "SUNDAY   : C L O S E D",
                "APPOINTMENT REQUIREMENT");

private static List<String> getSortedDates() {
    EnumSet<DayOfWeek> dayOfWeeks = EnumSet.allOf(DayOfWeek.class);
    return DATES.stream()
            .map(p -> dayOfWeeks.stream()
                    .filter(q -> p.startsWith(q.name()))
                    .findAny()
                    .map(r -> new SimpleImmutableEntry<>(r.ordinal(), p))
                    .orElse(new SimpleImmutableEntry<>(dayOfWeeks.size(), p)))
            .sorted(Comparator.comparing(SimpleImmutableEntry::getKey))
            .map(SimpleImmutableEntry::getValue)
            .collect(Collectors.toList());
}

public static void main(String[] args) {
    getSortedDates().forEach(System.out::println);
}

Thanks. Any sample code which works Java 6? – RKCY Jan 06 '19 at 02:03 — RKCY, Jan 06 '19 at 02:03

Convert arraylist elements order in sequence based on day

2 Answers2