Generating random date in a specific range in JAVA

Question

How to generate random dates in a specific range in JAVA? I have seen How do I generate random integers within a specific range in Java? link which is to generate random numbers.Is there similar/other kind of way to generate random date in JAVA?

Answer 1

Given that your question is unclear, I am expecting you are trying to generate random java.util.Date with given range.

Please note that java.util.Date contains date + time information.

Date in Java is represented by milliseconds from EPOCH. Therefore the easiest way to do what you want is, given d1 and d2 is Date, and d1 < d2 (in pseudo-code):

Date randomDate = new Date(ThreadLocalRandom.current()
                              .nextLong(d1.getTime(), d2.getTime()));

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If it is actually a "Date" (without time) that you want to produce, which is usually represented by LocalDate (in Java 8+, or using JODA Time).

It is as easy as, assume d1 and d2 being LocalDate, with d1 < d2 (pseudo-code):

int days = Days.daysBetween(d1, d2).toDays();
LocalDate randomDate = d1.addDays(
        ThreadLocalRandom.current().nextInt(days+1));

Answer 2

Try this

    LocalDate startDate = LocalDate.of(1990, 1, 1); //start date
    long start = startDate.toEpochDay();
    System.out.println(start);

    LocalDate endDate = LocalDate.now(); //end date
    long end = endDate.toEpochDay();
    System.out.println(start);

    long randomEpochDay = ThreadLocalRandom.current().longs(start, end).findAny().getAsLong();
    System.out.println(LocalDate.ofEpochDay(randomEpochDay)); // random date between the range

Answer 3

You can do something like this

    long random = ThreadLocalRandom.current().nextLong(startDate.getTime(), endDate.getTime());
    Date date = new Date(random);