Java String to Date

To convert a String to a Date in Java, you typically use the SimpleDateFormat class (for versions prior to Java 8) or the DateTimeFormatter class (from Java 8 onward, for LocalDate, LocalDateTime, and ZonedDateTime).

1. SimpleDateFormat (for Java 7 and earlier)

SimpleDateFormat is a subclass of DateFormat, and it’s used to parse and format Date objects in Java. It allows you to define a pattern to match the date format in the string.

Example:

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

public class StringToDateExample {
    public static void main(String[] args) {
        String dateString = "2024-01-01"; // Example date string
        
        // Define the date format that matches the string
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        
        try {
            // Convert the string to a Date object
            Date date = dateFormat.parse(dateString);
            System.out.println("Converted Date: " + date);
        } catch (ParseException e) {
            // Handle the case where the string doesn't match the format
            System.out.println("Invalid date format.");
        }
    }
}

Output: Converted Date: Mon Jan 08 00:00:00 GMT 2024

Explanation:

1. SimpleDateFormat is used to define the pattern “yyyy-MM-dd”, which corresponds to a year-month-day format.

2. The parse() method of SimpleDateFormat converts the string into a Date object.

3. If the string doesn’t match the format, a ParseException will be thrown, so it’s important to catch that exception.

2. DateTimeFormatter (Java 8 and later)

Starting from Java 8, the java.time package introduced the DateTimeFormatter class, which is the recommended way to handle date-time conversions. It’s more modern and less error-prone than SimpleDateFormat.

Example:

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

public class StringToDateExample {
    public static void main(String[] args) {
        String dateString = "2024-01-01"; // Example date string
        
        // Define the date format that matches the string
        DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
        
        // Convert the string to a LocalDate object
        LocalDate date = LocalDate.parse(dateString, dateFormatter);
        
        System.out.println("Converted Date: " + date);
    }
}

Output: Converted Date: 2024-01-01

Explanation:

1. DateTimeFormatter.ofPattern(“yyyy-MM-dd”) defines the format that matches the string.

2. LocalDate.parse(dateString, dateFormatter) parses the string into a LocalDate object.

3. Unlike SimpleDateFormat, DateTimeFormatter is immutable and thread-safe, making it a better choice for modern Java code.

3. Converting to LocalDateTime (if time is included)

If the input string includes both date and time (e.g., “2024-12-08 15:30”), you can convert it to a LocalDateTime.

Example:

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

public class StringToDateTimeExample {
    public static void main(String[] args) {
        String dateTimeString = "2024-01-01 10:15"; // Example date and time string
        
        // Define the format that matches the string
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
        
        // Convert the string to a LocalDateTime object
        LocalDateTime dateTime = LocalDateTime.parse(dateTimeString, dateTimeFormatter);
        
        System.out.println("Converted DateTime: " + dateTime);
    }
}

Output: Converted DateTime: 2024-01-01T10:15