集合对象可能包括任何数据类型的元素。

Collection objects might contain elements of any data types.

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在尝试向泛型集合(本例中为List)添加错误类型的元素时，清单2中的程序会生成编译时错误消息。

Listing 2 contains a program that generates the compilation-time error message that happens when you try to add the wrong type of element to a generic collection - a List in this case.

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与任何容器类型一样，可以使用内置的len方法查明集合中元素的数量。

As is the case with any container type, you can use the built-in len method to find out how many items are in the collection.

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