In this tutorial, we will explore how to determine the day of the week from a given date. This can be achieved using various methods and libraries, including Java’s built-in java.util.Calendar class, the SimpleDateFormat class, Joda-Time library, and the java.time package introduced in Java 8.
Using Java’s Built-in Classes
Before Java 8, you could use the java.util.Calendar class to determine the day of the week. Here is an example:
import java.util.Calendar;
import java.text.SimpleDateFormat;
public class Main {
public static void main(String[] args) throws Exception {
Calendar c = Calendar.getInstance();
c.set(2010, 1, 23); // Note: months are 0-based in Java
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK);
System.out.println("Day of week: " + dayOfWeek);
SimpleDateFormat sdf = new SimpleDateFormat("EEE");
String dayName = sdf.format(c.getTime());
System.out.println("Day name: " + dayName);
}
}
However, using Calendar and SimpleDateFormat can be cumbersome and error-prone due to their mutable nature and the complexities of date and time calculations.
Using Joda-Time
Joda-Time is a popular library for working with dates and times in Java. Although it’s now in maintenance mode, it’s still widely used. Here’s how you could use Joda-Time to find the day of the week:
import org.joda.time.DateTime;
import org.joda.time.DateTimeConstants;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;
public class Main {
public static void main(String[] args) {
DateTimeFormatter formatter = DateTimeFormat.forPattern("d/M/yyyy");
DateTime dt = formatter.parseDateTime("23/2/2010");
int dayOfWeek = dt.getDayOfWeek();
System.out.println("Day of week: " + dayOfWeek);
String dayName = dt.dayOfWeek().getAsShortText();
System.out.println("Day name: " + dayName);
}
}
Using Java 8’s java.time Package
Java 8 introduced the java.time package, which provides a comprehensive model for dates and times. It includes classes like LocalDate, LocalTime, LocalDateTime, ZonedDateTime, etc., and offers a more functional and thread-safe approach compared to the older date/time APIs.
Here’s how you can use java.time to determine the day of the week:
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.format.TextStyle;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/M/yyyy");
LocalDate date = LocalDate.parse("23/2/2010", formatter);
int dayOfWeek = date.getDayOfWeek().getValue();
System.out.println("Day of week: " + dayOfWeek);
String dayName = date.getDayOfWeek().getDisplayName(TextStyle.SHORT, Locale.US);
System.out.println("Day name: " + dayName);
}
}
Conclusion
Determining the day of the week from a given date can be accomplished through various methods and libraries in Java. While java.util.Calendar and Joda-Time are still viable options, the java.time package introduced in Java 8 offers a more modern, functional, and thread-safe approach to working with dates and times.
Advice
- For new projects or when updating existing code, consider using the
java.timepackage for its clarity, safety, and performance benefits. - Be mindful of the locale when formatting day names to ensure they are correctly represented in different languages and regions.
- Always prefer immutable date/time objects to avoid unintended modifications.