Kotlin - 如何在列表中查找重复值的数量？

Question

我有一个列表,例如:

val list = listOf("orange", "apple", "apple", "banana", "water", "bread", "banana")

如何检查苹果在此列表中重复的次数？

Answer 1

查找列表中所有重复值的一种方法是使用groupingBy然后过滤值> 1.例如

val list = listOf("orange", "apple", "apple", "banana", "water", "bread", "banana")
println(list.groupingBy { it }.eachCount().filter { it.value > 1 })

产量

{apple=2, banana=2}

Answer 2

list.count { it == "apple" }

文档:https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-list/,https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/count.html