Camel 转为 CamelCase，如 topic_comment -> TopicComment.

LowerCamel 转为 lowerCamelCase，如 TopicComment -> topicComment.

Plural 转为复数 user -> users.

Singular 转为单数 users -> user.

Snake 转为 snake_case，如 TopicComment -> topic_comment.

Letters && Numbers.

Only Letters.

Only Numbers.