对对列表进行排序 [英] Sorting a List of Pairs java

问题描述

我已经列出了成对的.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.

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.

我尝试了以下代码，但引发了不兼容类型的异常:无法推断类型变量T

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);

错误:

不兼容的类型:无法推断类型变量T (参数不匹配；方法参考无效 类Pair中的getKey方法不能应用于给定类型 必需:无参数 找到:对象 原因:实际参数和正式参数列表的长度不同)

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)

其中T，K，V是类型变量: T扩展了在方法compareInt(ToIntFunction)中声明的对象 K扩展在类Pair中声明的对象 V扩展了在类对中声明的对象

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

推荐答案

您需要帮助编译器为比较器推断适当的类型:

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));

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