Weekend filter for Java 8 LocalDateTime

Question

I want to write a boolean valued function which returns true if the given LocalDateTime falls between two specific points in time, false otherwise.

Specific

Answer 1

A simple TemporalQuery would do the trick:

static class IsWeekendQuery implements TemporalQuery{

    @Override
    public Boolean queryFrom(TemporalAccessor temporal) {
        return temporal.get(ChronoField.DAY_OF_WEEK) >= 5;
    }
}

It would be called like this (using .now() to get a value to test):

boolean isItWeekendNow = LocalDateTime.now().query(new IsWeekendQuery());

Or, specifically in UTC time (using .now() to get a value to test):

boolean isItWeekendNow = OffsetDateTime.now(ZoneOffset.UTC).query(new IsWeekendQuery());

Going beyond your question, there is no reason to create a new instance of IsWeekendQuery every time it is used, so you might want to create a static final TemporalQuery that encapsulates the logic in a lambda expression:

static final TemporalQuery IS_WEEKEND_QUERY = 
    t -> t.get(ChronoField.DAY_OF_WEEK) >= 5;

boolean isItWeekendNow = OffsetDateTime.now(ZoneOffset.UTC).query(IS_WEEKEND_QUERY);