本文介绍了Java中泛型通配符的使用规范，包括如何定义“in”变量和“out”变量，并提供了在不同场景下选择合适通配符的建议。
Wildcard Guidelines:
An "in" variable is defined with an upper bounded wildcard, using the extends keyword.
An "out" variable is defined with a lower bounded wildcard, using the super keyword.
In the case where the "in" variable can be accessed using methods defined in the Object class, use an unbounded wildcard.
In the case where the code needs to access the variable as both an "in" and an "out" variable, do not use a wildcard.
[url]http://docs.oracle.com/javase/tutorial/java/generics/wildcardGuidelines.html[/url]
JAVA 泛型FAQ
[url]http://www.angelikalanger.com/GenericsFAQ/FAQSections/ParameterizedTypes.html[/url]
An "in" variable is defined with an upper bounded wildcard, using the extends keyword.
An "out" variable is defined with a lower bounded wildcard, using the super keyword.
In the case where the "in" variable can be accessed using methods defined in the Object class, use an unbounded wildcard.
In the case where the code needs to access the variable as both an "in" and an "out" variable, do not use a wildcard.
[url]http://docs.oracle.com/javase/tutorial/java/generics/wildcardGuidelines.html[/url]
JAVA 泛型FAQ
[url]http://www.angelikalanger.com/GenericsFAQ/FAQSections/ParameterizedTypes.html[/url]
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