在框架内部的重要重构使用了泛型集合类代替非泛型的集合性。
Major refactoring internally to use generic collections instead of the non generic types.
通配符在类型系统中具有重要的意义，它们为一个泛型类所指定的类型集合提供了一个有用的类型范围。
Wildcards play an important role in the type system; they provide a useful type bound for the family of types specified by a generic class.
泛型类最常用于集合，如链接列表、哈希表、堆栈、队列、树等。
The most common use for generic classes is with collections like linked lists, hash tables, stacks, queues, trees, and so on.
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