Java Date & Time

SimpleDateFormat

The SimpleDateFormat class in Java is used to format and parse dates and times according to a specific pattern. It allows you to convert dates from their textual representation to a Date object and vice versa.

Example: Formatting a Date using SimpleDateFormat

java
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateFormatExample {
    public static void main(String[] args) {
        // Create a Date object representing the current date
        Date currentDate = new Date();

        // Define the desired date format pattern
        String pattern = "dd-MM-yyyy HH:mm:ss";

        // Create a SimpleDateFormat object with the specified pattern
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);

        // Format the date as a string
        String formattedDate = sdf.format(currentDate);

        // Display the formatted date
        System.out.println("Formatted Date: " + formattedDate);
    }
}

Explanation:
In this example, we first create a Date object representing the current date using new Date(). Next, we define the desired date format pattern "dd-MM-yyyy HH:mm:ss". The pattern consists of placeholders for day (dd), month (MM), year (yyyy), hours (HH), minutes (mm), and seconds (ss). We then create a SimpleDateFormat object with the specified pattern and use its format() method to convert the Date object to a formatted string. Finally, we print the formatted date to the console.

Current Date

Getting the current date in Java is quite straightforward. You can use the java.util.Date class in combination with java.util.Calendar or java.time.LocalDate from the Java 8 onward.

Example: Getting the Current Date

java
import java.util.Date;

public class CurrentDateExample {
    public static void main(String[] args) {
        // Approach 1: Using java.util.Date (legacy)
        Date currentDate1 = new Date();
        System.out.println("Current Date (Approach 1): " + currentDate1);

        // Approach 2: Using java.time.LocalDate (Java 8+)
        java.time.LocalDate currentDate2 = java.time.LocalDate.now();
        System.out.println("Current Date (Approach 2): " + currentDate2);
    }
}

Explanation:
In this example, we demonstrate two approaches to get the current date. The first approach uses the legacy java.util.Date class, and the second approach utilizes the modern java.time.LocalDate class introduced in Java 8. Both approaches will provide you with the current date when executed.

Compare Dates

Comparing dates is essential for many applications, especially when dealing with date-based operations. You can compare dates using the compareTo() method available in the java.util.Date class or the compareTo() method of the java.time.LocalDate class.

Example: Comparing Dates

java
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateComparisonExample {
    public static void main(String[] args) throws ParseException {
        // Date 1
        String dateString1 = "2023-07-15";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date date1 = sdf.parse(dateString1);

        // Date 2
        String dateString2 = "2023-07-20";
        Date date2 = sdf.parse(dateString2);

        // Compare dates using java.util.Date
        int comparisonResult = date1.compareTo(date2);

        if (comparisonResult < 0) {
            System.out.println("Date 1 is before Date 2.");
        } else if (comparisonResult > 0) {
            System.out.println("Date 1 is after Date 2.");
        } else {
            System.out.println("Date 1 and Date 2 are equal.");
        }
    }
}

Explanation:
In this example, we compare two dates using the java.util.Date class. We first parse two date strings "2023-07-15" and "2023-07-20" into Date objects using a SimpleDateFormat with the pattern "yyyy-MM-dd". Then, we use the compareTo() method to compare the two dates. The method returns a value less than 0 if the first date is before the second date, a value greater than 0 if the first date is after the second date, and 0 if the dates are equal. We then display the result based on the comparison.