B2 (final Number extendsGenericKey, final String extendsGenericValue) { if (this.extendsGenerics$key == null) { this.extendsGenerics$key = new java.util.ArrayList<Number>(); this.extendsGenerics$value = new java.util.ArrayList<String>(); } this.extendsGenerics$key.add(extendsGenericKey); this.extendsGenerics$value.add(extendsGenericValue); return self(); }