Java – returns 1 to 7 days of the week from any given date interval

I want to return a date map from the date interval:

>1 to 7 days:

From: "2016-02-09" to To: "2016-02-09" -> return : Tue
     From: "2016-02-09" to To: "2016-02-12" -> return : Tue,Wed,Thu,Fri
     From: "2016-02-02" to To: "2016-04-12" -> return : Tue,Fri,Sat,Sun,Mon (this should be sorted from Monday for the map)

>The sorted map (week starts on Monday), the returned date is the key string (string), and the value is always = true (Boolean), which will be reused for other purposes

I want to use joda time 2.8 1, but I don't know how to deal with date interval? I managed to get what I wanted, but only for one day:

String input = "2016-02-09";
DateTimeFormatter formatter = DateTimeFormat.forPattern( "yyyy-MM-dd" );
LocalDate localDate = formatter.parseLocalDate( input );
Locale locale = Locale.US;
DateTimeFormatter formatterOutput = DateTimeFormat.forPattern( "E" ).withLocale( locale );
String output = formatterOutput.print( localDate ); //Result = Tue

Solution

Joda time does not support (close) calendar date intervals, but only instantaneous intervals So here's a special solution:

LocalDate start = LocalDate.parse("2016-02-09");
LocalDate end = LocalDate.parse("2016-02-12");
if (start.isAfter(end))  {
    return Collections.emptyMap();
}

LocalDate current = start;
Map<Integer,Boolean> map = new TreeMap<>();

do {
    map.put(current.getDayOfWeek(),Boolean.TRUE);
    current = current.plusDays(1);
} while (!current.isAfter(end) && map.size() < 7);

LocalDate ref = new LocalDate(2016,2,7); // sunday
DateTimeFormatter f = DateTimeFormat.forPattern("E").withLocale(Locale.US);
StringBuilder sb = new StringBuilder();

for (int dayOfWeek : map.keySet()) {
    String output = f.print(ref.plusDays(dayOfWeek));
    sb.append(",");
    sb.append(output);
}
System.out.println(sb.delete(0,2).insert(0,"[").append(']').toString());
// [Tue,Fri]
return map;