无法在scala程序中打印

Question

以下scala代码显示没有输出请帮我纠正。我是scala的新手。我正在尝试打印Rational类实例。

object Test{

    def main() {
        var r = new Rational(2,3)
        println(r)
        println("Hello")
        //println(Rational(2,3).add(Rational(3,3)))
   }

}

class Rational(n:Int,d:Int)
{

    val num:Int =n
    val den:Int =d
    val sum :Int =num+den
    def add(that:Rational):Rational={
        return new Rational(num*that.den+den*that.num,den*that.den)
     }

     override def toString(): String =  num + "/" + den 

}

object Rational {
    def apply(n:Int,d:Int)=new Rational(n,d)
}

Answer 1

将def main()更改为def main(args: Array[String])，JVM无法识别没有正确参数类型的main方法