java - 对列表对进行排序 java

Question

这个问题已经有答案了:

Very confused by Java 8 Comparator type inference (4 个回答)

已关闭 3 年前。

我已经列出了成对的列表。我想先根据键对它们进行排序，如果键相同，则根据值进行排序。

我尝试了以下代码，但抛出了一个异常:不兼容的类型:无法推断类型变量 T

 List<Pair<Integer,Integer>> list = new ArrayList<>();
 list.sort(Comparator.comparingInt(Pair::getKey).thenComparingInt(Pair::getValue);

错误:

incompatible types: cannot infer type-variable(s) T (argument mismatch; invalid method reference method getKey in class Pair cannot be applied to given types required: no arguments found: Object reason: actual and formal argument lists differ in length)

where T,K,V are type-variables: T extends Object declared in method comparingInt(ToIntFunction) K extends Object declared in class Pair V extends Object declared in class Pair

Answer 1

您需要帮助编译器推断比较器的适当类型:

list.sort(Comparator.<Pair<Integer, Integer>>comparingInt(Pair::getKey).thenComparingInt(Pair::getValue));