Kevin Learn Kotlin：案例（一）四则运算

效果图

代码

/**
 * Created on 2021/11/26 13:48
 *
 * @author Gong Youqiang
 */
// 四则运算表达式计算器
fun main() {
    while (true) {
        println("=======请输入表达式=======")
        val input = readLine()
        try {
            input?.let {
                val result = calculate(it)
                println("$input = $result")
                println("是否继续使用（y/n）")
                val cmd = readLine()
                cmd?.let {
                    if (it == "n"){
                        exitProcess(-1)
                    }else {
                        // 继续使用
                    }
                }
            }
        }catch (e : Exception) {
            e.printStackTrace()
        }
    }
}

fun calculate(input: String): String {
    when {
        input.contains("+") -> {
            val nums = input.trim().split("+")
            return operate(nums[0].toDouble(),nums[1].toDouble(),"+").toString()
        }
        input.contains("-") -> {
            val nums = input.trim().split("-")
            return operate(nums[0].toDouble(),nums[1].toDouble(),"-").toString()
        }
        input.contains("*") -> {
            val nums = input.trim().split("*")
            return operate(nums[0].toDouble(),nums[1].toDouble(),"*").toString()
        }
        input.contains("/") -> {
            val nums = input.trim().split("/")
            return operate(nums[0].toDouble(),nums[1].toDouble(),"/").toString()
        }
        else -> {
            println("您输入的表达式有误")
            return "input error"
        }
    }
}

fun operate(nums: Double, nums2: Double,operate:String): Double {
    return when(operate){
        "+" -> nums + nums2
        "-" -> nums - nums2
        "*" -> nums * nums2
        "/" -> nums / nums2
        else -> 0.0
    }
}