August 2020
Intermediate to advanced
483 pages
11h 24m
Chinese
Content preview from Head First Kotlin程序设计
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你现在的位置 4 291
泛型
如何定义
MutableList
让我们看看在线文档如何定义
MutableList
以及它如何使用泛型。
我们将考虑两个关键环节：接口的声明和
add
方法的定义。
interface MutableList<E> : List<E>, MutableCollection<E> {
fun add(index: Int, element: E): Unit
//More code
}
理解集合文档（或者“
E
”的含义）
这是一个简单版的
MutableList
定义：
“
E
”
是声明
MutableList
时
所用实际类型的占位符
。
MutableList
继承于
List
和
MutableCollection
接
口
。
无论为
MutableList
指定哪种类型
（“
E
”
的值
）
都将自动作为
List
和
MutableC
ollection
的类型
。
“
E
”
是什么决定了可以向
MutableList
中添加哪些东西
。
MutableList
使用“
E
”作为你希望该集合保存和
返回的元素类型的替身。当你在文档中看到“
E
”
时，
你可以在大脑中进行查找
/
替换并将其转换成你希望的
任何类型。
例如，
MutableList<String>
表示在任何函数
或者变量中声明的“
E
”将变成“
String
”。而
MutableList<Duck>
意味着所有“
E
”的实例将全部
变成“
Duck
”。
让我们看看细节。
问
:
所以说MutableList不是一
个类
？
答
:
是的
，
它是接口
。
当你
使用
mutableListOf
方法创建
MutableList
时
，
系统创建了该接 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.