Question

我正在尝试将结果打印为双精度并收到以下错误：-

线程“ main”中的异常java.lang.NumberFormatException：对于输入字符串：“ kotlin.Unit”

我该如何解决？

def esm(data, ratio):
    X = series[data].values
    size = int(len(X) * ratio)


for data in ["col1", "col2", "col3", "col4"]:
    for ratio in [0.6, 0.7, 0.8, 0.9]:
        esm(data, ratio)
        # do something

Answer 1

问题出在这行

calculateWeight(150.0).toString().toDouble()

在calculateWeight函数中，因为没有返回类型，它将解析为默认值kotlin.Unit，您尝试使用toDouble()将其转换为 Double ，将其删除即可使用完美。而且异常在方法执行后发生，因为它发生在函数返回的值上。希望这会有所帮助

Answer 2

删除.toString().toDouble()部分，然后以这种方式实现以解决小数格式问题：

fun calculateWeight(bodyWeight: Double) {
    val mercury = bodyWeight * 0.38
    val venus = bodyWeight * 0.91
    val earth = bodyWeight * 1.00
    val mars = bodyWeight * 0.38
    val jupiter = bodyWeight * 2.34
    val saturn = bodyWeight * 1.06
    val uranus = bodyWeight * 0.92
    val neptune = bodyWeight * 1.19
    val pluto = bodyWeight * 0.06

    println("My body weight is %.2f pounds and on the different planets it equals:\n" +
            "Mercury: %.2f, \nVenus: %.2f, \nEarth: %.2f, " +
            "\nMars: %.2f, \nJupiter: %.2f, \nSaturn: %.2f, \nUranus: %.2f," +
            "\nNeptune: %.2f, \nPluto: %.2f".format(
                    bodyWeight, mercury, venus, earth, mars,
                    jupiter, saturn, uranus, neptune, pluto))
}

更好的是，这是一种更惯用的方式。

enum class Planet(val relativeGravity: Double) {
    Mercury(0.38),
    Venus(0.91),
    Earth(1.00),
    Mars(0.38),
    Jupiter(2.34),
    Saturn(1.06),
    Uranus(0.92),
    Neptune(1.19),
    Pluto(0.06);

    fun convert(weight: Double): Double {
        return weight * relativeGravity
    }
}

fun calculateWeight(bodyWeight: Double, unit: String = "pounds") {
    val prefix = "My body weight is $bodyWeight $unit and on the different planets it equals:\n"
    println(Planet.values().joinToString(prefix = prefix, separator = ",\n") { planet ->
        "%s: %.2f".format(planet.name, planet.convert(bodyWeight))
    })
}

错误：线程“ main”中的异常java.lang.NumberFormatException：对于输入字符串：“ kotlin.Unit”

2 个答案: