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- What does the question mark in Java generics' type parameter mean? 6 answers
- Java syntax <?> explanation 1 answer
Java泛型的类型参数中的问号是什么意思? 6个答案
Java语法 解释1答案
While doing some android app development, I encounter the parameter AdapterView< ? > test. My question is what exactly does < ? > mean or do because I also see it in many other places such as a Map where it is Map< String ,? >.
在做一些Android应用程序开发时,我遇到参数AdapterView
测试。我的问题究竟是什么? >意思还是因为我也在许多其他地方看到它,比如Map是Map
1 个解决方案
#1
3
In generic code, the question mark (?), called the wildcard, represents an unknown type.
在通用代码中,称为通配符的问号(?)表示未知类型。
The wildcard can be used in a variety of situations: as the type of a parameter, field, or local variable; sometimes as a return type.
通配符可用于各种情况:作为参数,字段或局部变量的类型;有时作为回归类型。
So in order to answer the question: it is a Wildcard-> Official Doc so you can handle classes event when you dont know the type.
所以为了回答这个问题:它是一个通配符 - >官方文档,所以当你不知道类型时你可以处理类事件。
#1
3
In generic code, the question mark (?), called the wildcard, represents an unknown type.
在通用代码中,称为通配符的问号(?)表示未知类型。
The wildcard can be used in a variety of situations: as the type of a parameter, field, or local variable; sometimes as a return type.
通配符可用于各种情况:作为参数,字段或局部变量的类型;有时作为回归类型。
So in order to answer the question: it is a Wildcard-> Official Doc so you can handle classes event when you dont know the type.
所以为了回答这个问题:它是一个通配符 - >官方文档,所以当你不知道类型时你可以处理类事件。