code: public static boolean isJavaxScriptingAvailable() {
      Object engine = null;
      try {
        Class<?> managerClass = Class.forName("javax.script.ScriptEngineManager");
        Method m = managerClass.getMethod("getEngineByMimeType", String.class);
        engine = m.invoke(managerClass.newInstance(), "text/javascript");
      } catch (ClassNotFoundException | NoSuchMethodException
          | IllegalAccessException | InvocationTargetException
          | InstantiationException e) {
        return false;
      }
  
      return engine != null;
    }
docs: ***********************************************************************
  Checks whether javax.script is available or not. Completely done per
  Reflection to allow compilation under Java 1.5
  
  @return true if javax.script is available; false otherwise
  **********************************************************************