Return a list of dates given an interval of dates and days of the week as booleans

Question

I'm trying to return a list of dates from these parameters :

LocalDate startDate
LocalDate endDate
Boolean monday ... sunday : booleans

For example :

startDate = 01/03/2016
endDate = 10/03/2016 (included)
Monday = true;
Tuesday = false;
Wednesday = false;
Thursday = true;
Friday = true;
Saturday = false;
Sunday = false;

List of dates returned : [03/03/2016, 04/03/2016, 07/03/2016, 10/03/2016]

Is there any libray i can use ? I've only managed to returned the dates between two dates, but i have no idea how to use the days also : (I'm using java 6)

public List<LocalDate> datesBetween(LocalDate start, LocalDate end) {
    List<LocalDate> ret = new ArrayList<LocalDate>();
    for (LocalDate date = start; !date.isAfter(end); date = date.plusDays(1)) {
        ret.add(date);
    }
    return ret;
}

Answer 1

Java SE 8 Date and Time

Listing 1

Standard Java getter conventions are used in order to obtain values from Java SE 8 classes, as shown in Listing 2.

LocalDate theDate = timePoint.toLocalDate();
Month month = timePoint.getMonth();
int day = timePoint.getDayOfMonth();
timePoint.getSecond();

Answer 2

The problem is the signature of your method. The fact that days are passed in as names makes it very hard to do anything generic; it means you will need lots of code to solve the problem. You may want to consider passing in an array of size 7, or a list of day names that correspond to 'true' (omitting the others).

If you were to pass in a set of integers ranging from 0 to 6, encoding that a day of the week is active if it is inside the set, you could iterate through your time range and check whether the day was passed as active, or not. You could use method like date.getDayOfWeek() and set.contains().

Answer 3

Avoid old date-time classes

Avoid the old date-time classes bundled with the earliest versions of Java, such as java.util.Date/.Calendar. They are poorly designed, confusing, and troublesome.

java.time

The java.time framework built into Java 8 and later supplants the old date-time classes. See Tutorial.

For use with Java 6 & 7, check out the ThreeTen-Backport project ('ThreeTen' refers to JSR 310 defining java.time). For Android specifically, see the Android wrapper around the Backport, ThreeTenABP.

The new classes include LocalDate for a date-only value without time-of-day and without time zone. Another handy class you need is the enum DayOfWeek. Use these objects rather than strings to make your code type-safe, self-documenting, and localization-ready.

Reminder: Java provides special high-performance Set and Map implementations for enums, EnumSet and EnumMap.

EnumSet<DayOfWeek> dayOfWeekSet = EnumSet.of( DayOfWeek.TUESDAY , DayOfWeek.THURSDAY );

Define a date interval.

LocalDate start = LocalDate.of( 2016 , Month.MARCH , 1 );
LocalDate stop = start.plusDays( 10 );

Define a collection to keep our targeted dates.

List<LocalDate> localDates = new ArrayList<>();

Loop the days in that interval. In date-time work we commonly use the Half-Open approach where the beginning in inclusive while the ending is exclusive.

LocalDate localDate = start;
while ( localDate.isBefore( stop ) ) {
    if ( dayOfWeekSet.contains ( localDate.getDayOfWeek() ) ) {
        localDates.add( localDate );
    }
    // Prepare for next loop.
    localDate = localDate.plusDays( 1 );
}

Dump to console.

System.out.println( "From: " + start + " to: " + stop + " the dates for days-of-week: " + dayOfWeekSet + " = " + localDates );

From: 2016-03-01 to: 2016-03-11 the dates for days-of-week: [TUESDAY, THURSDAY] = [2016-03-01, 2016-03-03, 2016-03-08, 2016-03-10]

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.