The plusDays() method of Period class in Java is used to add the days to this period. This method operates only on DAYS and does not affect other two YEAR, MONTH.
Syntax:
public Period plusDays(long daysToAdd)
Parameters: This method accepts a single parameter daysToAdd which is the number of days to be added from the period.
Return Value: It returns a Period based on provided period in the input adding the specified number of days. It must not be null.
Exceptions: It throws a ArithmeticException if numeric overflow occurs.
Below programs illustrate the above method:
Program 1:
// Java code to show the function plusDays()// to subtract the number of days from given periodsimport java.time.Period;import java.time.temporal.ChronoUnit;  public class PeriodClass {      // Function to subtract two given periods    static void addDays(Period p1, int daystoAdd)    {          System.out.println(p1.plusDays(daystoAdd));    }      // Driver Code    public static void main(String[] args)    {        // Defining first period        int year = 4;        int months = 11;        int days = 10;        Period p1 = Period.of(year, months, days);          int daystoAdd = 8;          addDays(p1, daystoAdd);    }} |
Output:
P4Y11M18D
Program 2: Period can be negative.
// Java code to show the function plusDays()// to subtract the number of days from given periodsimport java.time.Period;import java.time.temporal.ChronoUnit;  public class PeriodClass {      // Function to subtract two given periods    static void addDays(Period p1, int daystoAdd)    {          System.out.println(p1.plusDays(daystoAdd));    }      // Driver Code    public static void main(String[] args)    {          // Defining first period        int year = -4;        int months = -11;        int days = 0;        Period p1 = Period.of(year, months, days);          int daystoAdd = 8;          addDays(p1, daystoAdd);    }} |
Output:
P-4Y-11M8D
Reference: https://docs.oracle.com/javase/8/docs/api/java/time/Period.html#plusDays-long-
