1.创建 demo 工程：

Currently, scratches are supported only in Kotlin/JVM projects.

2.实际操作

val s = "Hello"
val t = "Kotlin"
val st = "$s$t"
println(st)

val a = 1
val b = 2
val c = a + b
println(c)

var sum = 0
for (i in 0..100)
    sum += i

println(sum)

for(i in 0..9)
    println(i)

参考文档：

https://kotlinlang.org/docs/tutorials/quick-run.html#using-scratches