Key<String> (@NotNull Project project) { Key<String> key = PROJECT_KEY_FOR_SUBSTITUTED_LANG_KEY.get(project); if (key == null) { synchronized (PROJECT_KEY_FOR_SUBSTITUTED_LANG_KEY) { key = PROJECT_KEY_FOR_SUBSTITUTED_LANG_KEY.get(project); if (key == null) { key = new Key<>("Substituted lang key for " + project.getName()); PROJECT_KEY_FOR_SUBSTITUTED_LANG_KEY.set(project, key); } } } return key; }