[英]Generics syntax: classes versus primitive data types
Why does this one does not work: 为什么这个不起作用:
ArrayList<LinkedList<int>>
where this one does: 这是做什么的:
ArrayList<LinkedList<Integer>>
??? ???
Because Java can only use classes (and not primitive types) and arrays (also arrays for primitives) for generics (between <
and >
). 因为Java只能将类(而不是基本类型)和数组(也可以是基本类型的数组)用于泛型(在
<
和>
之间)。
List<Integer> list;
That is also a reason why there are wrapper classes for primitive types: 这也是为什么原始类型有包装器类的原因:
int -> Integer
boolean -> Boolean
double -> Double
byte -> Byte
etc...
The argument in the <>
must be an object because those classes can only hold objects. <>
的参数必须是一个对象,因为这些类只能容纳对象。
int
is a primitive type, where as Integer
is simply a wrapper class for that type, so Integer
is the one that will work. int
是一种原始类型,其中Integer
只是该类型的包装器类,因此Integer
是可以工作的类型。
becuase the definition is LinkedList< T >
and only Object
can be here < T >
. 因为定义是
LinkedList< T >
并且只有Object
可以在此处< T >
。
int
is primitive type so LinkedList< int > - compile error
int
是原始类型,因此LinkedList< int > - compile error
Integer
is object LinkedList < Integer > - right one
Integer
是对象LinkedList < Integer > - right one
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.