scala的几个小程序

import java.util.function.BiConsumer

import scala.io.Source
import scala.util.Random

/**
* Created by fhqplzj on 16-7-16 at 上午10:47.
*/
object Hammock {
val sep = Array.fill(50)('*').mkString
var count = 0

def separate: Unit = {
println()
count += 1
println(s"${sep}example $count$sep")
println()
}

def main(args: Array[String]): Unit = {
/**
* 过滤所有的偶数
*/
separate
println((1 to 10).filter(_ % 2 == 0).mkString(" "))

/**
* 对序列中所有元素求和
*/
separate
println((1 to 10).reduce(_ + _))
println((1 to 10).fold(0)(_ + _))
println((1 to 10).sum)

/**
* 统计单词出现次数
*/
separate
val s = "hello world hello spark hello hadoop welcome to spark".split(" ")
println(s.groupBy(x => x).mapValues(_.length))

/**
* 将单词首字母大写
*/
separate
println(s.map(_.capitalize).mkString("\t"))

/**
* 最大值，最小值，求和
*/
separate
val list = List(2, 7, 1, 0, 5, 4)
println(list.max)
println(list.min)
println(list.sum)

/**
* 读取文件
*/
separate
val path = "/home/fhqplzj/temp/BeHappy/module2/src/main/scala/Hammock.scala"
Source.fromFile(path).getLines().toList.take(10).foreach(println)

/**
* 并行计算
*/
separate
println((1 to 100).par.sum)

/**
* 两个List求点积
*/
separate
val list1 = List.tabulate(10)(i => Random.nextInt(20))
val list2 = List.tabulate(10)(i => Random.nextInt(20))
println("list1 = " + list1)
println("list2 = " + list2)
val dotSum = (list1, list2).zipped.map(_ * _).sum
println("dotSum = " + dotSum)

/**
* 读取环境变量
*/
separate
System.getenv().forEach(new BiConsumer[String, String] {
override def accept(t: String, u: String): Unit = println(s"key=$t,value=$u")
})

/**
* 计算2到1000的所有素数
*/
separate
def sieve(xs: List[Int]): List[Int] = xs match {
case Nil => Nil
case x :: xs1 => List(x) ::: sieve(xs1.filter(_ % x != 0))
}
val nums = (2 to 1000).toList
val primes = sieve(nums)
println("primes = " + primes)

/**
* 快速排序
*/
separate
def qsort[T](xs: List[T])(implicit ord: Ordering[T]): List[T] = xs match {
case Nil => Nil
case x :: xs1 =>
val (left, right) = xs1.partition(ord.lt(_, x))
qsort(left)(ord) ::: List(x) ::: qsort(right)(ord)
}
println("list1 = " + list1)

/**
* 升序
*/
println(qsort(list1))

/**
* 降序
*/
println(qsort(list1)(Ordering.Int.reverse))
}
}