Handle iteration manually, by defining your own implementation of Iterable.

手动处理遍历，定义自己的Iterable实现。

youdao

Trying to get an Iterator on a Map fails at compile time — Maps don't implement the Iterable interface.

在编译时，尝试对 Map 获取 Iterator 会导致失败 — Map 并没有实现 Iterable 接口。

youdao

Extend an existing collection class that already implements Iterable (and therefore already supports for/in).

扩展现有的、已经实现了 Iterable（因此也就已经支持 for/in）的集合类。

youdao