TemporalAdjusters.next(DayOfWeek) and TemporalAdjusters.nextOrSame(DayOfWeek) are part of java.time.temporal.TemporalAdjusters class in Java. They adjust the date to the next, or the first occurrence of the specified DayOfWeek, or stay at the same date if it’s the desired DayOfWeek.

Here is how to use these methods:

package org.kodejava.datetime;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;

public class NextOrSameExample {
    public static void main(String[] args) {
        // Get the current date
        LocalDate date = LocalDate.now();
        System.out.println("Current date: " + date);

        LocalDate nextMonday = date.with(TemporalAdjusters.next(DayOfWeek.MONDAY));
        System.out.println("Next Monday: " + nextMonday);

        LocalDate nextOrSameFriday = date.with(TemporalAdjusters.nextOrSame(DayOfWeek.FRIDAY));
        System.out.println("Next Friday or same day if it's Friday: " + nextOrSameFriday);
    }
}

Output:

Current date: 2024-01-18
Next Monday: 2024-01-22
Next Friday or same day if it's Friday: 2024-01-19

In the above example:

• LocalDate.now() is used to get the current date.
• .with(TemporalAdjusters.next(DayOfWeek.MONDAY)) adjusts the date to the next Monday.
• .with(TemporalAdjusters.nextOrSame(DayOfWeek.FRIDAY)) adjusts the date to the next Friday or stays at the same date if it’s already Friday.

TemporalAdjusters.firstInMonth(DayOfWeek) and TemporalAdjusters.lastInMonth(DayOfWeek) methods are part of the java.time.temporal.TemporalAdjusters class. They adjust the date to the first or last occurrence of the specified DayOfWeek in the month.

Here’s an example of how to use these methods:

package org.kodejava.datetime;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;

public class FirstLastInMonthExample {
    public static void main(String[] args) {
        // Get the current date
        LocalDate date = LocalDate.now();
        System.out.println("Current date: " + date);

        LocalDate firstMondayInMonth = date.with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
        System.out.println("First Monday of this month: " + firstMondayInMonth);

        LocalDate lastFridayInMonth = date.with(TemporalAdjusters.lastInMonth(DayOfWeek.FRIDAY));
        System.out.println("Last Friday of this month: " + lastFridayInMonth);
    }
}

The output of the code snippet above:

Current date: 2024-01-18
First Monday of this month: 2024-01-01
Last Friday of this month: 2024-01-26

In this example:

• LocalDate.now()` is used to get the current date.
• .with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY)) adjusts the date to the first Monday of the current month.
• .with(TemporalAdjusters.lastInMonth(DayOfWeek.FRIDAY)) adjusts the date to the last Friday of the current month.

The TemporalAdjusters.firstDayOfYear() and TemporalAdjusters.firstDayOfNextYear() methods in Java are utilized to adjust a date to the first day of the current year and the first day of the next year respectively.

Here’s how to use these methods:

package org.kodejava.datetime;

import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;

public class FirstDayOfYearExample {
    public static void main(String[] args) {
        // Det the current date
        LocalDate date = LocalDate.now();
        System.out.println("Current date: " + date);

        LocalDate firstDayOfYear = date.with(TemporalAdjusters.firstDayOfYear());
        System.out.println("First day of this year: " + firstDayOfYear);

        LocalDate firstDayOfNextYear = date.with(TemporalAdjusters.firstDayOfNextYear());
        System.out.println("First day of next year: " + firstDayOfNextYear);
    }
}

In this example:

• LocalDate.now() is used to get the current date.
• .with(TemporalAdjusters.firstDayOfYear()) adjusts the date to the first day of the current year.
• .with(TemporalAdjusters.firstDayOfNextYear()) adjusts the date to the first day of the next year.

The output of the code snippet above:

Current date: 2024-01-18
First day of this year: 2024-01-01
First day of next year: 2025-01-01

The TemporalAdjusters.firstDayOfNextMonth() method is a useful method in java.time.temporal.TemporalAdjusters class in Java that adjusts the date to the first day of the next month.

Here’s an example usage:

package org.kodejava.datetime;

import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;

public class FirstDayOfNextMonthExample {
    public static void main(String[] args) {
        // Get the current date
        LocalDate date = LocalDate.now();

        // Adjust to the first day of next month
        LocalDate firstDayOfNextMonth = date.with(TemporalAdjusters.firstDayOfNextMonth());

        System.out.println("Current date: " + date);
        System.out.println("First day of next month: " + firstDayOfNextMonth);
    }
}

Output:

Current date: 2024-01-18
First day of next month: 2024-02-01

In this example, LocalDate.now() is used to get the current date. Then .with(TemporalAdjusters.firstDayOfNextMonth()) is used to adjust the date to the first day of the next month.