1、windows->preferences->java->Editor->Cotent Assist 中
auto-activetion中的Enable auto-activetion选项要勾选上
2、window->Preferences->Java->Editor->Content Assist->Advanced
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
3、重起eclipse,一切OK!!!