apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/ClassLoaderUtil.java/ClassLoaderUtil/isClassPresent
class ClassLoaderUtil:  public static boolean isClassPresent(String className) {
    try {
      Class.forName(className);
      return true;
    } catch (ClassNotFoundException ex) {
      // ignore expected exception
      return false;
    } catch (LinkageError ex) {
      // unexpected error, need to let the user know the actual error
      logger.error("Failed to load class: {}", className, ex);
      return false;
    }
  }