scala object隐式对象

package com.lhj.scala

import java.io.File
import scala.io.Source


object Test {
  abstract class A[T] {
      def add(x:T,y:T):T
    }
   
  abstract class B[T] extends A[T]{
      def unit:T
    }
   
  def main(args: Array[String]): Unit = {
    implicit object StringAdd extends B[String]{
      override def add(x:String,y:String) = x concat y
      override def unit:String = ""
    }

    implicit object IntAdd extends B[Int]{
      override def add(x:Int,y:Int) = x + y
      override def unit:Int = 0
    }
   
    def sum[T](x:List[T])(implicit b:B[T]): T =
      if (x.isEmpty) b.unit
      else b.add(x.head, sum(x.tail))
    println(sum(List(1,2,3,4,5)))
    println(sum(List("Spark","Hadoop","Akka")))
  }

}

--结果：
15
SparkHadoopAkka




package com.lhj.scala

import java.io.File
import scala.io.Source


object Test {
  def main(args: Array[String]): Unit = {
    val arr=Array(1,2,3,4)
    println(arr.head)
    println("---------------")
    for(x<-arr.tail){println(x)}
  }
}


--结果：
1
---------------
2
3
4