了解Java泛型。输入参数约定 [英] Understanding Java generics. Type parameter conventions
问题描述
最常用的类型参数名称是:
电子元素(广泛用于Java集合框架)
K - Key
数字
V - 价值
S,U,V等 - 第2,3,4类
我似乎不太明白每个字母对应的字母。我知道每个字母都只是一个约定,但是第二,第三和第四类型究竟意味着什么?我应该什么时候使用?在他们的官方教程网站上,它没有提供进一步的信息。
一些例子: 地图< K,V>
:地图通常将 V
分配给 K
EYS。
列表< E>
:列表包含电子
lements。这是一个被称为元素的约定。另一方面, T
在这里也是可以接受的。
Formatter< T>
:格式化程序可以格式化任何 T
ype。这不是一个真正的元素,也不是一个关键,也不是一个价值,所以 T
在这里是正确的。
三元组< T,U,V>
:任意类型的三元组。由于类型定义对后面将填充的类型没有任何了解,因此它只使用 T
作为第一种类型,接下来是按字母顺序排列的下一个字母。
The most commonly used type parameter names are:
E - Element (used extensively by the Java Collections Framework)
K - Key
N - Number
T - Type
V - Value
S,U,V etc. - 2nd, 3rd, 4th types
I don't seem to quite understand what exactly does every letter correspond to. I understand that each letter represents just a convention but what does 2nd, 3rd and 4th type mean exactly? When should I use what? On their official tutorials website it doesn't give further information.
Some examples:
Map<K, V>
: A map usually assignsV
alues toK
eys. These are special kinds of types, so they are used here.List<E>
: A list containsE
lements. It's a convention that they are called elements. On the other hand,T
would also be acceptable here.Formatter<T>
: A formatter can format anyT
ype. It's not really an element, nor a key, nor a value, soT
is the correct letter here.Triplet<T, U, V>
: A triplet for arbitrary types. Since the type definition does not know anything about the types that will be filled in later, it uses just theT
for the first type, followed by the next letters in alphabetical order.
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