How to Retrieve the First and Last Day of a Month Using ThreeTen's LocalDate

How can I extract the first and last days of a month from a LocalDate object using the ThreeTen library?

LocalDate date = LocalDate.of(2014, 2, 13); // Example LocalDate
LocalDate firstDay = date.withDayOfMonth(1);
LocalDate lastDay = date.withDayOfMonth(date.lengthOfMonth());

To find the first and last day of a month using the LocalDate class from the ThreeTen library in Java, you can utilize the methods provided by the LocalDate API, specifically `withDayOfMonth()` and `lengthOfMonth()`.

import org.threeten.bp.LocalDate;

public class MonthDaysExample {
    public static void main(String[] args) {
        LocalDate date = LocalDate.of(2014, 2, 13); // Any given date
        LocalDate firstDay = date.withDayOfMonth(1);
        LocalDate lastDay = date.withDayOfMonth(date.lengthOfMonth());

        System.out.println("First day: " + firstDay); // Output: First day: 2014-02-01
        System.out.println("Last day: " + lastDay);   // Output: Last day: 2014-02-28
    }
}

Causes

• Understanding the LocalDate class and its methods.
• Grasping how monthly days are calculated in Java.

Solutions

• Use the `withDayOfMonth(1)` method to get the first day of the month.
• Use the `withDayOfMonth(lengthOfMonth())` to get the last day of the month.

Mistake: Forgetting to import the necessary ThreeTen library classes.

Solution: Ensure you have the appropriate imports at the top of your Java file, such as `import org.threeten.bp.LocalDate;`.

Mistake: Assuming February always has 28 days without accounting for leap years.

Solution: Use `lengthOfMonth()` method which automatically accounts for leap years.