The ActionUtil class is a utility class in Logback that provides a convenient way to perform common actions such as adding and removing items from a list, or looking up a class by name. Here's an example of how it might be used:

import ch.qos.logback.core.joran.spi.ActionException;
import ch.qos.logback.core.spi.ContextAwareBase;
import ch.qos.logback.core.util.OptionHelper;

public class MyActionUtil extends ContextAwareBase {
    private String myClassName;
    private Class<?> myClass;

    public void setMyClassName(String myClassName) {
        this.myClassName = myClassName;
    }

    public void execute() throws ActionException {
        if (OptionHelper.isEmpty(myClassName)) {
            addError("className is null or empty.");
            return;
        }

        try {
            myClass = ActionUtil.classForName(myClassName);
        } catch (ClassNotFoundException e) {
            addError("Failed to load class [" + myClassName + "].", e);
            return;
        }

        // Do something with the class
        System.out.println("Successfully loaded class " + myClassName);
    }
}

In this example, MyActionUtil class uses the ActionUtil.classForName(myClassName) method to load a class by name, passed as a String in the myClassName field. It uses OptionHelper.isEmpty(myClassName) to check if the field is null or empty and addError("className is null or empty.") to report the error.

Also, addError("Failed to load class [" + myClassName + "].", e) is used to report if the class is not found, and if the class is found System.out.println("Successfully loaded class " + myClassName) is used to print the class name

It is important to notice that this is just an example of how the ActionUtil class can be used and how it's classForName() method can be used to load a class by name. The implementation of your application may vary depending on your specific requirements and the way you want to use the class.