java / groovy从列表中收集具有指定值的元素(java/groovy collect elements from list with specified value)

java / groovy从列表中收集具有指定值的元素(java/groovy collect elements from list with specified value)

我有一对配对列表，需要找到距离最小的所有配对。

class Pair { ... distance ... } List<Pair> pairs = findAllDistances() // list that holds all pairs with distances double minDistance = pairs.distance.min() // finds minimal distance, for example 1.0 // pairs list contains 15 elements with distance = 1.0 List<Pair> minDistancePairs = pairs.collect { it.distance = minDistance }

为什么我在计算后得到minDistancePairs = null ？

I have a list of pairs and need to find all pairs with minimal distance.

class Pair { ... distance ... } List<Pair> pairs = findAllDistances() // list that holds all pairs with distances double minDistance = pairs.distance.min() // finds minimal distance, for example 1.0 // pairs list contains 15 elements with distance = 1.0 List<Pair> minDistancePairs = pairs.collect { it.distance = minDistance }

Why I get minDistancePairs = null after calculations?

最满意答案

简单的'='是赋值，double'=='是比较。 假设您要收集距离等于'minDistance'的所有对，您应该：

List<Pair> minDistancePairs = pairs.collect { it.distance == minDistance }

Simple '=' is assignation, double '==' is comparison. Assuming you want to collect all pairs where the distance is equal to 'minDistance', you should do:

List<Pair> minDistancePairs = pairs.collect { it.distance == minDistance }