scala隐式转换实例

关于scala语言的隐式转换特性，其他博客的介绍已有不少，这里只是附上一个写代码过程中实际用到的例子：

1. 扩充Traversable特征的功能

package com.flute.collection

import java.util

import scala.collection.mutable.ListBuffer

/**
  * Created by xpli on 02/06/16.
  */
class RichTraversable[A](traver: Traversable[A]) {

  def groupCount(): Traversable[(A, Int)] = traver.map((_, 1)).groupBy(_._1).map(g => (g._1, g._2.size))

  def distinctBy[K](f: A => K): Traversable[A] = {
    val newBuilder = new ListBuffer[A]
    val seen = collection.mutable.HashSet[K]()
    for (x <- traver) {
      val k = f(x)
      if (!seen(k)) {
        newBuilder += x
        seen += k
      }
    }

    newBuilder
  }

  def distinctCountBy[K](f: A => K, expr: A => Boolean = expr => true): Int = {
    var totalCount = 0
    val seen = collection.mutable.HashSet[K]()
    for (x <- traver) {
      if (expr(x)) {
        val k = f(x)
        if (!seen(k)) {
          totalCount += 1
          seen += k
        }
      }
    }

    totalCount
  }

  //  def distinctCountBy[K](f: A => K): Int = {
  //    var totalCount = 0
  //    val seen = collection.mutable.HashSet[K]()
  //    for (x <- traver) {
  //      val k = f(x)
  //      if (!seen(k)) {
  //        totalCount += 1
  //        seen += k
  //      }
  //    }
  //
  //    totalCount
  //  }

  def shuffle(): Traversable[A] = {
    import collection.JavaConversions._

    val jList: util.List[A] = new util.ArrayList[A]()
    traver.foreach(jList.add)

    java.util.Collections.shuffle(jList)

    jList
  }

  def safeReduce(op: (A, A) => A): Option[A] = {
    if (traver.isEmpty) {
      None
    } else {
      Some(traver.reduce(op))
    }
  }

  def saveToFile(path: String): Unit = com.flute.utils.FileUtil.write(traver, path)


}

定义隐式转换函数

package com.flute.common

import com.flute.collection.{PairTraversable, RichTraversable, SeqJoinWrapper, StrSeqWrapper}

/**
  * Created by xpli on 2016/5/28.
  */
object Implicits {
implicit def toRichTraver[A](traver: Traversable[A]) = new RichTraversable[A](traver)


}

使用示例：

object test {

  def main(args: Array[String]) {

//保存保存到文件
import com.flute.common.Implicits._
val lst = Traversable("qaz", "wsx", "123")
lst.saveToFile("test.txt")

//随机排序
lst.shuffle().foreach(println)

}

}