@Override
  public boolean isStopped() {
    return this.stopped;
  }
Base class for the hfile cleaning function inside the master. By default, only the
{@link TimeToLiveHFileCleaner} is called.
<p>
If other effects are needed, implement your own HFileCleanerDelegate and add it to the
configuration "hbase.master.hfilecleaner.plugins", which is a comma-separated list of fully
qualified class names. The <code>HFileCleaner</code> will build the cleaner chain in order the
order specified by the configuration.
</p>
<p>
For subclasses, setConf will be called exactly <i>once</i> before using the cleaner.
</p>
<p>
Since {@link BaseHFileCleanerDelegate HFileCleanerDelegates} are created in HFileCleaner by
reflection, classes that implements this interface <b>must</b> provide a default constructor.
</p>
hbase-server/src/main/java/org/apache/hadoop/hbase/master/cleaner/BaseHFileCleanerDelegate.java