Step by Step solution about How to resolve the algorithm Last Friday of each month step by step in the Java programming language

This Java program calculates and prints the dates of the last Fridays in each month of a given year, passed as the first argument to the program. Let's break down the code:

1. Input Processing:

   • int year = Integer.parseInt(args[0]);: Parses the year from the first command-line argument and stores it in the year variable.

2. Calendar Setup:

   • GregorianCalendar c = new GregorianCalendar(year, 0, 1);: Creates a GregorianCalendar object c for the specified year. It initializes the calendar to January 1st of that year.

3. Loop Through Months:

   • for (String mon : new DateFormatSymbols(Locale.US).getShortMonths()): Iterates through the short names of the months for the US locale.

4. Month-End Calculations:

   • int totalDaysOfMonth = c.getActualMaximum(Calendar.DAY_OF_MONTH);: Gets the total number of days in the current month.
   • c.set(Calendar.DAY_OF_MONTH, totalDaysOfMonth);: Sets the calendar to the last day of the current month.

5. Days to Roll Back:

   • int daysToRollBack = (c.get(Calendar.DAY_OF_WEEK) + 1) % 7;: Calculates the number of days to roll back from the last day of the month to get to the last Friday. This is done by finding the day of the week for the last day (0-based index) and adding 1 to it. The result is then taken modulo 7 to find the number of days to roll back.

6. Last Friday's Date:

   • int day = totalDaysOfMonth - daysToRollBack;: Calculates the day of the last Friday by subtracting the days to roll back from the total days in the month.
   • c.set(Calendar.DAY_OF_MONTH, day);: Sets the calendar to the calculated last Friday's date.

7. Output:

   • System.out.printf("%d %s %d\n", year, mon, day);: Prints the calculated last Friday's date in the format "year month day".

8. Advance to Next Month:

   • c.set(year, c.get(Calendar.MONTH) + 1, 1);: Advances the calendar to the first day of the next month.

import java.text.*;
import java.util.*;

public class LastFridays {

    public static void main(String[] args) throws Exception {
        int year = Integer.parseInt(args[0]);
        GregorianCalendar c = new GregorianCalendar(year, 0, 1);

        for (String mon : new DateFormatSymbols(Locale.US).getShortMonths()) {
            if (!mon.isEmpty()) {
                int totalDaysOfMonth = c.getActualMaximum(Calendar.DAY_OF_MONTH);
                c.set(Calendar.DAY_OF_MONTH, totalDaysOfMonth);

                int daysToRollBack = (c.get(Calendar.DAY_OF_WEEK) + 1) % 7;

                int day = totalDaysOfMonth - daysToRollBack;
                c.set(Calendar.DAY_OF_MONTH, day);

                System.out.printf("%d %s %d\n", year, mon, day);

                c.set(year, c.get(Calendar.MONTH) + 1, 1);
            }
        }
    }
}