利用できるスクリプトエンジンを列挙する

 ScriptEngineManager mgr = new ScriptEngineManager();

 List<ScriptEngineFactory> factories = mgr.getEngineFactories();
  for(ScriptEngineFactory f:factories){
   List<String> engNames = f.getNames();
   for(String name: engNames) {
     System.out.printf("Engine : %s\n", name);
   }
  }