Скачать или смотреть How to Convert String to Date with Milliseconds in Java

Learn how to convert a String to Date format in Java, ensuring that milliseconds are accurately represented using SimpleDateFormat.
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This video is based on the question https://stackoverflow.com/q/63631068/ asked by the user 'Mohamed Drira' ( https://stackoverflow.com/u/14093511/ ) and on the answer https://stackoverflow.com/a/63631432/ provided by the user 'schrom' ( https://stackoverflow.com/u/2217962/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Convert String to Date with Milliseconds in Java

When working with dates in Java, especially when they include milliseconds, it can be a bit tricky. Many developers often encounter a common issue: the milliseconds seem to vanish when converting a date stored as a string into a Date object. In this guide, we'll explore this issue and provide a clear solution to convert a string containing date and time information—down to the milliseconds—into a Java Date object accurately.

Understanding the Problem

In Java, the SimpleDateFormat class is a powerful tool for date and time manipulation. However, developers have noted that when they attempt to convert a string like "2020-08-27T10:06:07.413" into a Date, the milliseconds do not show up in the expected output.

Consider the following sample code:

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Output

When running the above code, you might see an output like this:

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Notice how the milliseconds are missing!

Why Are the Milliseconds Missing?

The confusion arises from how the Date class represents time. By default, the Date object stores time as milliseconds. However, when you print the Date object using System.out.println(), Java utilizes the toString() method of the Date class to format the output. This method does not include milliseconds and produces output in the following format:

[[See Video to Reveal this Text or Code Snippet]]

To truly see the milliseconds, we need to print the date using the formatter we originally defined.

Solution: Displaying the Date with Milliseconds

To display the Date with milliseconds included, you can simply use the formatter to format the date object back into a string, as demonstrated below:

[[See Video to Reveal this Text or Code Snippet]]

Expected Output

Implementing this line in your code will produce an output like:

[[See Video to Reveal this Text or Code Snippet]]

Now the milliseconds are correctly displayed as part of the formatted date string.

Summary

In summary, when working with the Java Date class and converting string dates that include milliseconds:

The SimpleDateFormat allows for precise conversion, including milliseconds.

Use System.out.println(formatter.format(dateFormatter)); to see the complete date, including milliseconds.

By following these steps, you can ensure your date representations in Java retain the necessary detail for accurate time management and comparison. If you have any further questions or issues regarding date conversion in Java, feel free to leave a comment below!