Here is an example of using the LogbackServiceProvider class from the logback.classic.spi package in Java:

import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.classic.spi.LogbackServiceProvider;
import ch.qos.logback.core.Appender;
import org.slf4j.LoggerFactory;

public class Example {
    public static void main(String[] args) {
        LogbackServiceProvider provider = (LogbackServiceProvider) LoggerFactory.getILoggerFactory();
        Appender<ILoggingEvent> appender = provider.getAppender("console");
        if (appender != null) {
            System.out.println("Appender found: " + appender.getName());
        } else {
            System.out.println("Appender not found.");
        }
    }
}

In this example, LogbackServiceProvider class is used to retrieve an appender by its name. We use the LoggerFactory.getILoggerFactory() method to get the service provider instance and then cast it to LogbackServiceProvider. We can then call the getAppender method on the service provider, passing in the name of the appender that we want to retrieve.

In this case, we are looking for an appender named "console", but if the appender is not found, the getAppender method will return null.

This example would work if you have already defined "console" appender in the logback configuration file.

You need to add logback classic library in the classpath to use this example.