import java.text.SimpleDateFormat;

import java.time.LocalDate;

import java.time.format.DateTimeFormatter;

import java.util.Calendar;

import java.util.Date;

public class DateTimeExample {

public static void main(String[] args) {

// Example date: December 30, 2024

// This date is particularly interesting because it's at the end of the year

// where yyyy and YYYY can show different results

System.out.println("Date Format Demonstration - yyyy vs YYYY\n");

// Java 7 style using SimpleDateFormat

System.out.println("Java 7 Style (using SimpleDateFormat):");

demonstrateJava7Style();

System.out.println();

// Java 8+ style using DateTimeFormatter

System.out.println("Java 8+ Style (using DateTimeFormatter):");

demonstrateModernStyle();

}

private static void demonstrateJava7Style() {

// Create a Calendar instance for December 30, 2024

Calendar cal = Calendar.getInstance();

cal.set(2024, Calendar.DECEMBER, 30); // Month is 0-based

Date date = cal.getTime();

// yyyy - Calendar year

SimpleDateFormat sdfYear = new SimpleDateFormat("yyyy-MM-dd");

System.out.println("yyyy format: " + sdfYear.format(date));

// YYYY - Week-based year

SimpleDateFormat sdfWeekYear = new SimpleDateFormat("YYYY-MM-dd");

System.out.println("YYYY format: " + sdfWeekYear.format(date));

System.out.println("Note: In Java 7, SimpleDateFormat's YYYY might not handle week-based years correctly");

}

private static void demonstrateModernStyle() {

// Create a LocalDate for December 30, 2024

LocalDate date = LocalDate.of(2024, 12, 30);

// yyyy - Calendar year

DateTimeFormatter formatterYear = DateTimeFormatter.ofPattern("yyyy-MM-dd");

System.out.println("yyyy format: " + date.format(formatterYear));

// YYYY - Week-based year

DateTimeFormatter formatterWeekYear = DateTimeFormatter.ofPattern("YYYY-MM-dd");

System.out.println("YYYY format: " + date.format(formatterWeekYear));

System.out.println("Note: In Java 8+, YYYY correctly handles week-based years");

System.out.println("- yyyy represents the calendar year");

System.out.println("- YYYY represents the week-based year (ISO week date)");

System.out.println(" December 30, 2024 falls in the first week of 2025,");

System.out.println(" hence YYYY shows 2025 instead of 2024");

}

}