将嵌套的ArrayList转换为List Java [英] Converting nested ArrayList into List Java

问题描述

我有此方法

public List<List<Stat>> ConvertReportCases (ArrayList<ArrayList<Stat>> stats)

这是一个接口实现，返回类型为List<List<Stat>>.一般来说，如何将嵌套的ArrayList转换为Java中的List?

It is an interface implementation where the return type is a List<List<Stat>>. In general how do I convert from a nested ArrayList to List in Java?

谢谢

修改 感谢您的建议，我可以将参数作为List传递，但是由于调用者必须将其作为List传递而将是错误的，而在我的特殊情况下，我可以使用不同的版本(多态性)来检查此问题.

Edit Thanks for the suggestions I could make my parameter passed as List but then it would be wrong since the caller will have to pass it as List, whereas in my particular case I could have different versions (polymorphism) to check this issue.

推荐答案

真的，不需要转换.

如果您无法触摸列表的声明，则应将方法签名更改为此.它使用通配符.

public List<? extends List<Stat>> convertReportCases(List<? extends List<Stat>> stats);

---

但是，最干净的方法是将方法签名更改为

---

However, the most clean way would be to change the method signature to

public List<List<Stat>> convertReportCases(List<List<Stat>> stats);

并将列表声明为

List<List<Stat>> list = new ArrayList<List<Stat>>();
for (List<Stat> sublist : list) {
    sublist = new ArrayList<Stat>();
}

如果使用List方法，则可以，不需要任何转换.而且由于ArrayList是-a List，并且实际上仅对List方法有用，所以您应该没事！

If you use List methods, you will be ok, there will be no converting needed. And since ArrayList is-a List and is practically only useful for its List methods, you should be ok!

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