void clearImages(long currentTime) {
      boolean all = currentTime <= 0;
      for (Iterator<GraphicsConfiguration> it = cachedMap.keySet().iterator(); it.hasNext(); ) {
        GraphicsConfiguration cfg = it.next();
        Cached c = cachedMap.get(cfg);
        if (all || currentTime - c.touched > 2 * 60 * 1000L) {
          it.remove();
          LOG.info(logPrefix(cfg, c.image) + "image flushed" +
                   (all ? "" : "; untouched for " + StringUtil.formatDuration(currentTime - c.touched)));
          c.image.flush();
        }
      }
    }
void clearImages(long currentTime)