Also, they contain no elements except the new service method, again because the methods will be merged into existing classes.

而且，除非是新的服务方法，否则它们不包含元素，还有就是因为这些方法将被合并入现有类。

youdao

But maps lack some of the features expected of structured data: they have no real "type" (without added metadata) and, unlike classes, they can't be extended with new behavior.

但是映射缺乏一些结构化数据的预期功能：它们没有真实的“类型”(在不添加元数据的情况下)，不像类那样，它们不能通过新的行为扩展。

youdao

Conventional abstraction mechanisms of general purpose programming languages such as methods and classes, are no longer sufficient for creating new abstraction layers.

通用语言中的传统的抽象机制，如方法和类，已不足以满足建立新的抽象层次的需要。

youdao

For 30 years--until 2000--there were no new classes of antibiotics approved.

FORBES: Magazine Article

Dame Sally said no new classes of antibiotics had been introduced since 1987 whereas new pathogens were emerging every year, and existing bugs were developing resistance to current treatments.

BBC: Health

So far, there is no prevision to open new classes.

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