Here is an example of how you might use the UnsynchronizedAppenderBase class from the logback library in Java:

import ch.qos.logback.core.UnsynchronizedAppenderBase;
import ch.qos.logback.classic.spi.ILoggingEvent;

public class MyAppender extends UnsynchronizedAppenderBase<ILoggingEvent> {

    @Override
    protected void append(ILoggingEvent event) {
        // do something with the event, for example, write to a file
        String message = event.getFormattedMessage();
        System.out.println(message);
    }
}

In this example, we create a new class MyAppender that extends UnsynchronizedAppenderBase. The class is parameterized with ILoggingEvent. The UnsynchronizedAppenderBase is an abstract class that provides a basic implementation of the Appender interface. To use it we have to override append method, where we can put our custom logic to process the logging event. In this example, we simply print the message of the event to the console.

You can then use an instance of this class in your logging configuration to send log events to it.

<configuration>
  <appender name="MY_APPENDER" class="com.example.MyAppender">
    <!-- additional appender configuration options -->
  </appender>

  <root level="debug">
    <appender-ref ref="MY_APPENDER" />
  </root>
</configuration>

This XML configuration will send all log events with a level of "debug" or higher to the MyAppender instance.