Here is an example of how to use the Filter class from the logback library in Java:

import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.filter.Filter;
import ch.qos.logback.core.spi.FilterReply;
import org.slf4j.LoggerFactory;

public class Example {
    public static void main(String[] args) {
        Logger logger = (Logger) LoggerFactory.getLogger("ExampleLogger");
        logger.addFilter(new ExampleFilter());

        logger.debug("This is a debug message.");
        logger.info("This is an info message.");
        logger.warn("This is a warn message.");
        logger.error("This is an error message.");
    }
}

class ExampleFilter extends Filter<ILoggingEvent> {

    @Override
    public FilterReply decide(ILoggingEvent event) {
        if (event.getLevel().isGreaterOrEqual(Level.ERROR)) {
            return FilterReply.ACCEPT;
        } else {
            return FilterReply.DENY;
        }
    }
}

This example creates an instance of the custom Filter class ExampleFilter and adds it to the logger, so that all the events logged through it will go through the filter. The filter implements the decide method which will check if the log level is greater or equal than ERROR, and it will accept the event and pass it through, otherwise it will deny it and the event will not be logged.

Please note that

• You should import the relevant classes for logback
• The above code is just an example and it does not include the full context of a logging application.
• The provided code is missing the import statments and methods to get logger instance