Here's an example of how to use the PatternLayoutEncoder class from the Logback library to format log messages using a pattern:

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.encoder.PatternLayoutEncoder;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.ConsoleAppender;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MyClass {
  private static final Logger logger = LoggerFactory.getLogger(MyClass.class);

  public static void main(String[] args) {
    // Create a new LoggerContext
    LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();

    // Create a new ConsoleAppender
    ConsoleAppender<ILoggingEvent> consoleAppender = new ConsoleAppender<>();
    consoleAppender.setContext(context);

    // Create a new PatternLayoutEncoder and set it as the encoder for the ConsoleAppender
    PatternLayoutEncoder encoder = new PatternLayoutEncoder();
    encoder.setContext(context);
    encoder.setPattern("%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n");
    consoleAppender.setEncoder(encoder);

    // Start the ConsoleAppender
    consoleAppender.start();

    // Add the ConsoleAppender to the root logger
    context.getLogger("ROOT").addAppender(consoleAppender);

    // Log some messages
    logger.info("Hello, world!");
    logger.error("This is an error");

    // Stop the ConsoleAppender
    consoleAppender.stop();
  }
}

In this example, the PatternLayoutEncoder is being used to format log messages using a pattern. The pattern used is "%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n", this pattern includes information such as the timestamp, thread, level, logger name and message.

The ConsoleAppender writes the log messages to the console.

You can customize the pattern to fit your needs by using different conversion words, check the logback documentation for more details.

It's important to notice that this is just one example of how the PatternLayoutEncoder can be used and is just one of several encoders provided by logback