java / groovy从列表中收集具有指定值的元素

Question

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？

Answer 1

你需要findAll，而不是收集

List<Pair> minDistancePairs = pairs.distance.min().with { min ->
    pairs.findAll { it.distance == min }
}

Answer 2

简单＆＃39; =＆＃39;是分配，双重＆= 39; ==＆＃39;比较。假设您要收集距离等于＆＃39; minDistance＆＃39;的所有对，您应该这样做：

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