val data = mutableMapOf<String,String>(
    "username" to "王菲",
    "age" to "18"
)

如果这里面还希望加上if else 是否可以呢，可以的

val age = "18"
val data = mutableMapOf<String, Any>(
    "username" to "王菲",
    "age" to age.toInt(),
    "adult" to if (age.toInt() >= 18) {
        "成年人"
    } else {
        "未成年人"
    }
)