社区版仅支持有限数量的插件。如果我没记错的话，只有Ultimate版本支持类图插件。

The community edition only supports a limited number of plugins. The class diagram plugin is only supported in the Ultimate edition if I remember correctly.

您可以随时尝试IntelliJ Ultimate（或RubyMine）的30天免费试用。

You can always try a 30-day free trial of IntelliJ Ultimate (or RubyMine).