Question

所以我今天下午开始学习Scala，当我尝试使用标准scalac Sqrt.scala和scala Sqrt运行我的程序时，很快就出现了停止点：

java.lang.NoSuchMethodException: Sqrt.main is not static
    at scala.reflect.internal.util.ScalaClassLoader$class.run(ScalaClassLoader.scala:68)
    at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:101)
    at scala.tools.nsc.CommonRunner$class.run(ObjectRunner.scala:22)
    at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:39)
    at scala.tools.nsc.CommonRunner$class.runAndCatch(ObjectRunner.scala:29)
    at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:39)
    at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:65)
    at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:87)
    at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:98)
    at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:103)
    at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

这是我的Sqrt.scala的代码：

class Sqrt {
  val PRECISION = 0.01

  def abs(d: Double): Double =
    if (d >= 0) d else -d

  def isCloseEnough(guess: Double, x: Double): Boolean =
    abs(guess * guess - x) < PRECISION

  def improve(guess: Double, x: Double): Double =
    (x/guess + guess)/2

  def iter(guess: Double, x: Double): Double =
    if(isCloseEnough(guess, x)) guess
    else iter(improve(guess, x), x)

  def sqrt(x: Double): Double =
    iter(1, x)

  def main(args: Array[String]) {
    println(sqrt(16))
  }
}

有人可以提出解释吗？

Answer 1

object Sqrt代替class Sqrt

看看Scala开始使用：http://www.scala-lang.org/documentation/getting-started.html

此外，不推荐使用您正在使用的main函数的语法，它应该是： def main(args: Array[String]):Unit = {}。

启动Scala程序时出现NoSuchMethodException

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