Why Timestamp cannot be used in place of Date in Java? Example

In Java, both Timestamp and Date are classes that represent points in time, but they have some differences in their usage and behavior. 

While it is possible to use Timestamp in place of Date in certain scenarios, there are cases where it is not recommended. Here's an example to illustrate the limitations of using Timestamp in place of Date:

import java.sql.Timestamp;
import java.util.Date;

public class Main {
    public static void main(String[] args) {
        Date date = new Date();
        Timestamp timestamp = new Timestamp(date.getTime());

        // Example 1: Date to Timestamp
        System.out.println("Date: " + date);
        System.out.println("Timestamp: " + timestamp);

        // Example 2: Timestamp to Date
        Date convertedDate = new Date(timestamp.getTime());
        System.out.println("Converted Date: " + convertedDate);

        // Example 3: Timestamp limitations
        timestamp.setNanos(123456789);
        System.out.println("Modified Timestamp: " + timestamp);
    }
}

In Example 1, we convert a Date object to a Timestamp using the getTime() method. The conversion is straightforward and allows you to work with the more specialized features of Timestamp, such as nanosecond precision. 

In Example 2, we convert the Timestamp back to a Date using the getTime() method. This conversion is possible and allows you to retrieve a Date object from a Timestamp. However, there are certain limitations when using Timestamp in place of Date, as demonstrated.

In Example 3. The Timestamp class has additional fields to store nanosecond precision, but the Date class does not. When you modify the nanosecond field of a Timestamp, it does not affect the Date object created from it. In other words, the nanosecond precision is lost when converting a Timestamp to a Date. 

It's important to note that Timestamp is primarily used in the context of the JDBC API for working with databases that support timestamp values with nanosecond precision. 

If you're not working with such databases or don't require nanosecond precision, it is generally recommended to use the Date class or other modern date and time APIs introduced in Java 8, such as java.time.LocalDate or java.time.LocalDateTime, for improved clarity, simplicity, and consistency.