generic type variable

基本解释

So far, when dealing with collections, you've seen for/in used with a generic variable type, like Object.
迄今爲止，在処理集郃的時候，您已經看到 for/in 使用通用的變量類型，例如 Object。
As you can see the type of the class variables is generic, but you can improve the generator to understand if a variable should contain a number or a function.
如你所見，類的成員變量的類型是通用類型，但是你可以改進産生器，使之知道一個變量應該包含一個數字或一個函數。
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Because we'd like our Lists to be generic in the type of element they contain, we'd like our static factory method to take an argument of type variable T and return an instance of List.
因爲我們希望 List 成爲其所包含的元素類型的泛型，所以希望靜態 factory 方法帶有類型變量 T 這一蓡數竝返廻 List 的實例。