code: public boolean hasClass(String name) {
          byte[] b = classesFound.get(name);
          Boolean found = b == null ? null : b.length > 0;
          if (found != null)
              return found;
  
          try {
              // try dynamic jar assets
              String path = name.replace('.', '/') + ".class";
              b = findInJarAssets(path);
              // try the file system
              if (b == null)
                  b = findInFileSystem(path);
          }
          catch (Exception ex) {
              logger.severeException(ex.getMessage(),  ex);
          }
          found = b != null;
          classesFound.put(name, found ? b : new byte[0]);
          return found;
      }
docs: Looks for classes in Jar assets or on the prop-specified classpath.
  Results are cached, so Jar/CP changes require app redeployment.