Scala入门
学习之前需要了解几个内容：
1.Scala目前的地位
大数据而生
2.Scala可以做什么
spark底层代码是scala编写，所以可以编写spark
3.Scala与java的区别
Scala是一个函数式语言，在某种意义上来讲所有函数都是数值。
开始学习
一.Scala基础
1.需要先集成scala环境
如何用Intellij IDEA写scala 搭建scala开发环境_百度经验
2.直接上代码了（必须有c或者java基础）
import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.Map
object Hello {
def main(args:Array[String]):Unit = {
println("hehe")
val x = 10
val result = {
if (x>5)
{1}
else
{
"haha"
}
}
println(result)
}
for(i <-1 to 3 ;
j <-1 to 3 ) {
println("i=" +i +"j=" +j)
}
val v = for( i <-1 to 10 ) yield i *10
println(v)
val s = Array(1,2,3)
val t = for(i <-s ) yield i *10
for(k <-0 until t.length)
println(t(k));
def m1(x:Int,y:Int) :Int =x *y
println(m1(8,9))
val r = 1 to 10
val f1 = (x:Int) =>x *10
val f2 = (y:Int) =>y *10
val w = r.map(f1)
for(i <-0 until w.length )
print(w(i))
val u =r.map(_ *100)
for(i <-0 until w.length )
print(u(i))
print(u.toBuffer)
valfunc :Int =>String = { y =>y.toString }
println(func(10))
val reverse :(Int,Double) =>(Double,Int) = { (x,y) =>(y,x)}
print(reverse(3,3.01))
// 神奇的下划线
val m2 = m1 _
print(m2(3,4));
val arr3 = Array(1,2,3)
val arr4 = for(i <-arr3) yield i*10
print(arr4.toBuffer)
val ab = ArrayBuffer[Int]()
ab += 1
ab ++= Array(2,3)
ab.insert(0,0)
ab += 4
print(ab)
val ac = ab.filter( _ %2 ==0 ).map(_ *10).sortWith(_>_)
print(ac)
val map1 = Map("i" -> 1)
val map2 = Map("j" -> 2)
map1("k") = 3
map1 += ("o" -> 4)
map2("j")=10
println("map:"+map1.toBuffer)
println("map:"+map2.toBuffer)
//元组从1开始
val vs = (1,"spark",3.0)
print(vs._2)
val pa = ("l",3)
map2 += pa
map2 += (("h",10),("g",11))
println("map:"+map2.toBuffer)
val list1= List(1,2.3)
val list2=0 :: list1
println(list1)
println(list2)
}
二.spark之一个RDD
import org.apache.spark.{SparkConf, SparkContext}
object HigthRdd {
def main(args:Array[String]):Unit = {
val conf = new SparkConf().setAppName("high-rdd")
val sc = new SparkContext(conf)
/*
val rdd1 = sc.parallelize(List(1,2,3,4,5,6,7,8,9), 2)
val func = (index: Int, iter: Iterator[(Int)]) => {
iter.toList.map(x => "[partID:" +index + ", val: " + x + "]").iterator
}
rdd1.mapPartitionsWithIndex(func).collect
*/
def func1(index:Int, iter:Iterator[(Int)]) :Iterator[String] = {
iter.toList.map(x =>"[partID:" +index +", val: " +x +"]").iterator
}
val rdd1 = sc.parallelize(List(1,2,3,4,5,6,7,8,9), 2)
val a= rdd1.mapPartitionsWithIndex(func1).collect()
print(a)
}
}
二.spark之worldcount
object Worlds {
def main(args:Array[String]) {
val words = List("haha hehe heihei heihei", "hehe heihei")
/* val line = words.map(_.split(" ")).flatten
println(line.toBuffer)
*/
val a1 = words.flatMap(_.split(" "))
println(a1)
val a2 = a1.map((_, 1))
println(a2)
val a3 = a2.groupBy(_._1)
println(a3)
val a4 = a3.map(t =>(t._1, t._2.size))
println(a4)
val a5 = a4.toList.sortBy(_._2).reverse
println(a5)
/* val aa = words.flatMap(_.split(" ")).map((_, 1)).groupBy(_._1).map(t => (t._1, t._2.size)).toList.sortBy(_._2).reverse
println(aa)*/
val aa= words.flatMap(_.split(" ")).map((_,1)).groupBy(_._1).map( t =>(t._1,t._2.size)).toList.sortBy(_._2)
println("aa"+aa)
}
【Scala入门】}
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