Core Date-Time Classes in Java 8

Java's traditional date and time handling prior to Java 8 presented challenges due to unintuitive design and thread safety concerns in java.util.Date and java.util.Calendar. The Java 8 Date-Time API introduced immutable, thread-safe alternatives including LocalDate, LocalTime, and LocalDateTime.

Date Handling with LocalDate

LocalDate represents date information without time components in ISO-8601 format (yyyy-MM-dd).

Instantiating Date Objects

import java.time.LocalDate;

public class DateCreation {
    public static void main(String[] args) {
        LocalDate current = LocalDate.now();
        System.out.println("Current date: " + current);
        
        LocalDate custom = LocalDate.of(2023, 12, 25);
        System.out.println("Custom date: " + custom);
        
        LocalDate fromText = LocalDate.parse("2024-01-01");
        System.out.println("Parsed date: " + fromText);
    }
}

Date Manipulation Techniques

public class DateOperations {
    public static void main(String[] args) {
        LocalDate today = LocalDate.now();
        
        int currentYear = today.getYear();
        int currentMonth = today.getMonthValue();
        int currentDay = today.getDayOfMonth();
        System.out.printf("Year: %d, Month: %d, Day: %d%n", currentYear, currentMonth, currentDay);
        
        LocalDate futureWeek = today.plusWeeks(1);
        System.out.println("Next week: " + futureWeek);
        
        LocalDate pastMonth = today.minusMonths(1);
        System.out.println("Previous month: " + pastMonth);
        
        boolean leapCheck = today.isLeapYear();
        System.out.println("Leap year? " + leapCheck);
    }
}

Time Management with LocalTime

LocalTime handles time-of-day values without date information, using HH:mm:ss format.

Creating Time Instances

import java.time.LocalTime;

public class TimeCreation {
    public static void main(String[] args) {
        LocalTime current = LocalTime.now();
        System.out.println("Current time: " + current);
        
        LocalTime specified = LocalTime.of(14, 45, 30);
        System.out.println("Specified time: " + specified);
        
        LocalTime fromString = LocalTime.parse("09:15:00");
        System.out.println("Parsed time: " + fromString);
    }
}

Time Operation Methods

public class TimeOperations {
    public static void main(String[] args) {
        LocalTime now = LocalTime.now();
        
        int hours = now.getHour();
        int minutes = now.getMinute();
        int seconds = now.getSecond();
        System.out.printf("Hours: %d, Minutes: %d, Seconds: %d%n", hours, minutes, seconds);
        
        LocalTime later = now.plusHours(2);
        System.out.println("Two hours later: " + later);
        
        LocalTime earlier = now.minusMinutes(15);
        System.out.println("Fifteen minutes prior: " + earlier);
        
        LocalTime reference = LocalTime.of(17, 0);
        boolean beforeCheck = now.isBefore(reference);
        boolean afterCheck = now.isAfter(reference);
        System.out.printf("Before 5 PM? %s, After 5 PM? %s%n", beforeCheck, afterCheck);
    }
}

Combined Date-Time with LocalDateTime

LocalDateTime integrates date and time components using the format yyyy-MM-ddTHH:mm:ss.

DateTime Object Creation

import java.time.LocalDateTime;

public class DateTimeCreation {
    public static void main(String[] args) {
        LocalDateTime current = LocalDateTime.now();
        System.out.println("Current date-time: " + current);
        
        LocalDateTime custom = LocalDateTime.of(2023, 8, 20, 16, 30);
        System.out.println("Custom date-time: " + custom);
        
        LocalDateTime parsed = LocalDateTime.parse("2023-10-31T19:00:00");
        System.out.println("Parsed date-time: " + parsed);
    }
}

DateTime Maniuplation

public class DateTimeOperations {
    public static void main(String[] args) {
        LocalDateTime now = LocalDateTime.now();
        
        int year = now.getYear();
        int month = now.getMonthValue();
        int day = now.getDayOfMonth();
        int hour = now.getHour();
        int minute = now.getMinute();
        int second = now.getSecond();
        System.out.printf("Year: %d, Month: %d, Day: %d, Hour: %d, Minute: %d, Second: %d%n", 
                          year, month, day, hour, minute, second);
        
        LocalDateTime tomorrow = now.plusDays(1);
        System.out.println("Next day: " + tomorrow);
        
        LocalDateTime previousHour = now.minusHours(1);
        System.out.println("Previous hour: " + previousHour);
        
        LocalDate dateComponent = now.toLocalDate();
        LocalTime timeComponent = now.toLocalTime();
        System.out.println("Date component: " + dateComponent);
        System.out.println("Time component: " + timeComponent);
    }
}

Integrating Date and Time Components

public class ComponentIntegration {
    public static void main(String[] args) {
        LocalDate datePart = LocalDate.of(2024, 5, 15);
        LocalTime timePart = LocalTime.of(13, 45);
        LocalDateTime combined = LocalDateTime.of(datePart, timePart);
        System.out.println("Combined date-time: " + combined);
        
        LocalDate extractedDate = combined.toLocalDate();
        LocalTime extractedTime = combined.toLocalTime();
        System.out.println("Extracted date: " + extractedDate);
        System.out.println("Extracted time: " + extractedTime);
    }
}