Sorting a List of Pairs java [duplicate]

问题

This question already has answers here:

Very confused by Java 8 Comparator type inference (4 answers)

Closed 5 months ago.

I've List with Pairs in it. I want to sort them according to the keys first and if keys are same then sort according to the values.

I tried following code but throws an exception incompatible types: cannot infer type-variable(s) T

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

Error :

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

回答1:

You need to help the compiler infer the appropriate type for the comparator:

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

来源：https://stackoverflow.com/questions/57624889/sorting-a-list-of-pairs-java