Collect conditional items while steaming in kotlin-CodePudding

In Kotlin code, I have a list of objects and while processing it via filter and map I want to collect items of particular interest. And discard others.

For example, I am using foreach loop as below. Is it possible to make it better by using map instead of foreach?

fun main() {

val exceptionRequests = mutableListOf<String>()

listOf<String>("Name1", "Name2", "Name3")
    .filter {
        it.length > 2
    }
    .forEach {
        try {
            if (it == "Name2") {
                throw Exception(it)
            }
        } catch (exception: Exception) {
            exceptionRequests.add(it)
        }
    }

println(exceptionRequests) // This prints `Name2`.
}

CodePudding user response：

Why do you compare it and throw an Exception and then add that in the catch block?

You can derive exceptionRequests as follow:

val exceptionRequests = listOf<String>("Name1", "Name2", "Name3")
.filter {
  it.length > 2 && it == "Name2"
}

CodePudding user response：

Perhaps I'm misunderstanding your question, but your current example can simply be written as

val exceptionRequests = listOf<String>("Name1", "Name2", "Name3")
    .filter {
        it.length > 2
    }
    .filter {
        it == "Name2"
    }

println(exceptionRequests) // This prints `Name2`.

(if you want to keep these filters separate - alternatively, you can combine them to a single filter)