如何在list中获取最大双倍？只有一个输出，使用Kotlin

Question

我试过使用.maxBy .max()和collection.Max，但我只能打印出每个元素都是最大的。

    val fileName = "src/products.txt"
    var products = HashMap<Int, Pair<String, Double>>()

    var inputFD = File(fileName).forEachLine {
    var pieces = it.split(",")

    println("Item#     Description     Price")
    println("-----     -------------   ------")
       for ( (pro,ducts) in products.toSortedMap() ) {

          var pax = mutableListOf(ducts).maxBy { it -> it.second }
          var highest = listOf<Double>(ducts.second).max()

          println("The highest priced record is ${highest}")
       }

文件是这样设置的(111, shoe, 9.99)

产出是这样的最高价记录是[(裤子，89.99)]最高价记录是[(鞋子，49.99)]。

Answer 1

你试图在for-loop中打印值，因此它是为每个产品打印的。而且变量在循环中每次都会被初始化，所以每个值都会是最大值。

这里是正确的方法。请注意，你可以在不使用可变变量的情况下解决它。

val fileName = "src/products.txt"
val products = File(fileName).readLines()  //read all lines from file to a list
        .map { it.split(",") }     // map it to list of list of strings split by comma
        .map { it[0] to it[1].toDouble() } // map each product to its double value in a Pair
        .toMap() // convert list of Pairs to a Map

println("Item#     Description     Price")
println("-----     -------------   ------")

products.keys.forEachIndexed { index, desc ->
    println("$index\t$desc\t${products[desc]}")
}
println("The highest priced record is ${products.maxBy { it.value }}")