摘要:
抽象类Advertisemnt中有一个抽象方法/***ReturnsanIDwhichidentifiesthis{@codeAdvertisement}asuniquelyas*possible.ThisIDistypicallyusedastheprimarykeyforindexingof*theAdvertisementwithindatabases.*<p/>*Eachadvertisementsub-classmustchooseanappropriateimplementation*whichreturnscanonicalandrelativelyuniqueIDv 阅读全文