ここが変だよScalaさん ref: https://qiita.com/poad1010/items/19e2c16a8877e82379f3

file1.txt

a - 1
a - 2
a - 3
b - 4
b - 5
b - 6
c is empty
false

scala

val data = Map("a" -> Seq(1,2,3), "b" -> Seq(4,5,6), "c" -> Seq(), "d" -> Seq(7,8,9))

def conv(data: Map[String, Seq[Int]]): Boolean = {
    data.foreach(kv => {
        val key = kv._1
        val value = kv._2
        if (value.isEmpty) {
            println(s"${key} is empty")
            return false // ここで親のconvメソッドの戻り値が返せてしまう
        }
        value.map(v => {
            s"${key} - ${v}"
        })
        .foreach(println)
    })
    true
}

println(conv(data))