Here is an example of a class extending TimeBasedRollingPolicy in Logback:

import ch.qos.logback.core.rolling.TimeBasedRollingPolicy;

public class MyTimeBasedRollingPolicy extends TimeBasedRollingPolicy {

    @Override
    public void start() {
        // additional initialization code
        super.start();
    }

    @Override
    public void rollover() {
        // rollover logic
    }
    
    @Override
    public String getActiveFileName() {
        // return the active file name
    }
}

This class is an example of a custom rolling policy in Logback, which is used to determine when log files should be rolled over. The class is based on time. The start method is overridden to perform additional initialization. The rollover method is overridden to define the specific rollover logic. Also, the getActiveFileName method is overridden to return the active file name that is currently being written to.

This class is extending TimeBasedRollingPolicy, which is a rolling policy that rolls over the file when the current period of time elapses. It uses a TimeBasedFileNamingAndTriggeringPolicy object to compute the filename of the next rollover file, as well as the next rollover time.