code: public synchronized long getLastModified( Artifact artifact )
          throws IOException, ArtifactNotFoundException
      {
          Map<String, Map<String, Map<Artifact, Content>>> artifactMap = contents.get( artifact.getGroupId() );
          Map<String, Map<Artifact, Content>> versionMap = ( artifactMap == null ? null : artifactMap.get( artifact.getArtifactId() ) );
          Map<Artifact, Content> filesMap = ( versionMap == null ? null : versionMap.get( artifact.getVersion() ) );
          Content content = ( filesMap == null ? null : filesMap.get( artifact ) );
          if ( content == null )
          {
              if ( artifact.isSnapshot() && artifact.getTimestamp() == null && filesMap != null )
              {
                  Artifact best = null;
                  for ( Map.Entry<Artifact, Content> entry : filesMap.entrySet() )
                  {
                      Artifact a = entry.getKey();
                      if ( artifact.equalSnapshots( a ) && ( best == null || best.compareTo( a ) < 0 ) )
                      {
                          best = a;
                          content = entry.getValue();
                      }
                  }
                  if ( content == null )
                  {
                      throw new ArtifactNotFoundException( artifact );
                  }
              }
              else
              {
                  throw new ArtifactNotFoundException( artifact );
              }
          }
          return content.getLastModified();
      }
docs: {@inheritDoc}