When should you prefer DateTimeFormatter and when should you avoid it?

DateTimeFormatter is a powerful class in Java that allows for flexible date and time formatting. You should prefer using DateTimeFormatter when you need a customizable, locale-sensitive formatting mechanism for dates and times. It provides a readable way to convert between different formats, which is particularly useful when dealing with user inputs or displaying dates in various locales.

However, you may want to avoid DateTimeFormatter if your application does not require such flexibility or if you are working with simple date formats that can be easily achieved with simpler classes or methods, such as SimpleDateFormat (though this is not recommended due to its thread-safety issues). In addition, if performance is a critical concern and you are formatting dates in a tight loop where the format remains constant, you may prefer to use a pre-defined formatter to avoid the overhead of creating new instances.