DateTimeFormatter and SimpleDateFormat are two classes in Java that can be used to format dates and times.

SimpleDateFormat is a class that has been part of the Java API for a long time, and it is used to parse and format dates according to a given format string. It is based on the java.util.Calendar class, which is a legacy date and time API.

DateTimeFormatter, on the other hand, is a newer class that was introduced in Java 8 as part of the java.time package. It is an immutable formatter that can be used to parse and format dates and times in a more modern and flexible way. DateTimeFormatter is based on the newer java.time API, which is the recommended way to work with dates and times in Java.

Here are a few key differences between SimpleDateFormat and DateTimeFormatter:

• SimpleDateFormat is not thread-safe, while DateTimeFormatter is thread-safe. This means that you can safely use a DateTimeFormatter object from multiple threads, but you need to be careful when using SimpleDateFormat from multiple threads.

• SimpleDateFormat is based on the legacy java.util.Calendar API, while DateTimeFormatter is based on the newer java.time API. The java.time API is generally considered to be more modern and flexible than the java.util.Calendar API.

• SimpleDateFormat requires you to specify a format string when you create a new object, while DateTimeFormatter allows you to specify the format as a pattern of letters and symbols. For example, you can use DateTimeFormatter.ofPattern(“yyyy-MM-dd HH:mm:ss”) to create a formatter that formats dates in the same way as SimpleDateFormat(“yyyy-MM-dd HH:mm:ss”).

Overall, DateTimeFormatter is generally a better choice than SimpleDateFormat for formatting dates and times in Java. It is more thread-safe, more flexible, and based on the newer and recommended java.time API.