网上搜索了一下，方法集中在两种:
1. Window->Preferences->Java->Editor->Hovers 将[Variable Values]选择即可，如果[Combined Hover]已经勾选，取消并勾选[Variable Values]
2. 右击工程->properties->Java Compiler->选中 "add variable attributes to generated class (used by the debugger)” 选项即可