Change Date Format In A Java String

In Java, to change the format of a date that is represented as a String, you typically need to parse the original string into a Date object (or LocalDate, LocalDateTime, etc.), and then format it into a new string with the desired format. You can use SimpleDateFormat (for older versions of Java) or the DateTimeFormatter (for Java 8 and newer) to accomplish this.

Using SimpleDateFormat (Java 7 and earlier)

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

public class Main {
    public static void main(String[] args) {
        try {
            // Original date string
            String originalDateStr = "2025-01-20";

            // Define the original format
            SimpleDateFormat originalFormat = new SimpleDateFormat("yyyy-MM-dd");

            // Parse the original string to a Date object
            Date date = originalFormat.parse(originalDateStr);

            // Define the new format
            SimpleDateFormat newFormat = new SimpleDateFormat("MM/dd/yyyy");

            // Format the Date object into the new string format
            String newDateStr = newFormat.format(date);

            System.out.println("Original Date: " + originalDateStr);
            System.out.println("New Date Format: " + newDateStr);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Output:

Original Date: 2025-01-20
New Date Format: 01/20/2025

In this example:

• We define the original date format (yyyy-MM-dd).
• We parse the original string into a Date object.
• We then format that Date object into a new string using a different format (MM/dd/yyyy).

Using DateTimeFormatter (Java 8 and newer)

For modern Java (Java 8 and later), you should use the DateTimeFormatter class, which is part of the java.time package.

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class Main {
    public static void main(String[] args) {
        // Original date string
        String originalDateStr = "2025-01-20";

        // Define the original format
        DateTimeFormatter originalFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");

        // Parse the string to a LocalDate object
        LocalDate date = LocalDate.parse(originalDateStr, originalFormatter);

        // Define the new format
        DateTimeFormatter newFormatter = DateTimeFormatter.ofPattern("MM/dd/yyyy");

        // Format the LocalDate object into the new string format
        String newDateStr = date.format(newFormatter);

        System.out.println("Original Date: " + originalDateStr);
        System.out.println("New Date Format: " + newDateStr);
    }
}

Output:

Original Date: 2025-01-20
New Date Format: 01/20/2025

In this example:

• We define the original date format (yyyy-MM-dd) using DateTimeFormatter.
• We parse the original string into a LocalDate object.
• We then format the LocalDate object into a new string using a different format (MM/dd/yyyy).