code: public void clearCache() {
          BufferedImage cache = cachedImage == null ? null : cachedImage.get();
          if (cache != null) {
              cache.flush();
          }
          cacheCleared = true;
          if (!isCacheable()) {
              cachedImage = null;
          }
      }
docs: <p>Call this method to clear the cacheable. This may be called whether there is
  a cacheable being used or not. If cleared, on the next call to <code>paint</code>,
  the painting routines will be called.</p>
  
  <p><strong>Subclasses</strong>If overridden in subclasses, you
  <strong>must</strong> call super.clearCache, or physical
  resources (such as an Image) may leak.</p>