Week numbers in Java
To get the current ISO 8601 week number in Java, use the following code snippet:
import java.time.LocalDate;
import java.time.temporal.IsoFields;
int week = LocalDate.now().get(IsoFields.WEEK_OF_WEEK_BASED_YEAR);
* Ensure your system or application regional settings are set to follow ISO 8601 standards (weeks start on Monday) if the output varies.
Step-by-Step Instructions
- Import java.time.LocalDate and java.time.temporal.IsoFields.
- Call LocalDate.now().get(IsoFields.WEEK_OF_WEEK_BASED_YEAR).
- For the matching ISO year use IsoFields.WEEK_BASED_YEAR.
Good to Know
Avoid the legacy java.util.Calendar week fields: they depend on the default Locale and can silently use Sunday-start US numbering. The java.time IsoFields API is locale-independent and always ISO 8601.