菜单window->Preferences->Java->Editor->Content Assist->Enable auto activation 选项要打上勾 (并将auto activation triggers for java:skdfjldf.)
window->Preferences->Java->Editor->Content Assist->Advanced 上面的选项卡Select the proposal kinds contained in the \'default\' content assist list: 中把 Java Proposals 选项打上勾就可以了。