PluginHolder { public static PluginHolder getInstance() { if (instance == null) { throw new IllegalStateException("The PluginHolder has not yet been built. Please call build() before calling get."); } return instance; } private  PluginHolder(); static PluginHolder build(File[] pluginJars); static PluginHolder getInstance(); ArrayList<NotifierPlugin> getNotifierPlugins(); ArrayList<SecurityPlugin> getSecurityPlugins();  }
@Test public void testGetInstance() { System.out.println("getInstance"); PluginHolder result = PluginHolder.getInstance(); assertNotNull(result); result = PluginHolder.getInstance(); assertNotNull(result); }