Java编译器如何确定“方法不适用”？

Question

When using a wildcards some methods (eg ArrayList.set ) cannot be used and return an error message similar to

The method set(int, capture#3-of ?) in the type List is not applicable for the arguments (int, String)

I have read why this is the case and would like to know how this is done. That is how does the compiler know that some methods are applicable (eg List.get(int) ) but others are not?

Answer 1

所有适用的规则在Java语言规范＃15.12中 。

Answer 2

Compiler assgins special tokens ( capture#3-of ? ) to each occurence of wildcard and use regular method applicability rules ( JLS 15.12.2 ).

Since captures of wildcards are not compatilbe with other types and with other captures, "method not applicable" is produced.