Here is an example of a class using CachingDateFormatter in Logback:

import ch.qos.logback.core.CoreConstants;
import ch.qos.logback.core.pattern.util.CachingDateFormatter;

public class MyClass {

    private CachingDateFormatter cachingDateFormatter;

    public MyClass() {
        cachingDateFormatter = new CachingDateFormatter("yyyy-MM-dd HH:mm:ss.SSS");
    }

    public void doSomething() {
        String formattedDate = cachingDateFormatter.format(System.currentTimeMillis());
        // use formattedDate
    }
}

This class is an example of using CachingDateFormatter in Logback. CachingDateFormatter is a utility class that provides a way to format date and time in a caching way. It's used to improve performance by formatting the date once and reusing it instead of formatting it every time it's needed.

In this example, MyClass has a constructor that initializes a CachingDateFormatter object by passing the date format "yyyy-MM-dd HH:mm:ss.SSS" to its constructor. The doSomething method uses the format method of the CachingDateFormatter class to format the current time and returns the result as a string.

It is important to note that CachingDateFormatter is a utility class that provides a way to format date and time in a caching way. It's used to improve performance by formatting the date once and reusing it instead of formatting it every time it's needed. The CachingDateFormatter class is thread-safe and it's recommended to use it instead of creating multiple instances of SimpleDateFormat in a multi-threaded environment.