大数据学习-scala（1）

1.scala是纯面向对象的

如1，在java中是基本类型，不是对象，

1在scala中是对象，有方法

2.scala有函数

3.val定义不可变变量

4.var定义可变变量

var name = "Scala"

name = "Spark"

5.没有指定类型，可以手动指定类型

val age :Int = 2;

6.多个相同变量

var age1,age2,age3 = 0;

7.to

0.t0(5)

自动进行隐式转换

8.+号是方法

1.+（1）

9.scala中没有++，--

10.条件判断

 val age = 19

age: Int = 19

scala> if(age >= 18) "adult"

11.scala的最后一行就是返回值

12.打印输出println("spark")

13.print("\n spark")

14.printf()

15.readLine

16.if else

17.while

18.for(i<-0 to element)println(i)

19.定义函数

进入paste模式

：paste

val n = 10

def f1:Int = {

  for(i<-1 to 10){

    if(i==n)return i

    println(i)

  }

return 0

}

// Exiting paste mode, now interpreting.

n: Int = 10

f1: Int

scala> f1

1

2

3

4

5

6

7

8

9

res0: Int = 10

scala> println _

res1: () => Unit = <function0>

scala> def f2 = println

f2: Unit

scala> f2("good")

<console>:9: error: Unit does not take parameters

              f2("good")

                ^

scala> def f3(param1 : String,param2:int=20) = param1+param2

<console>:7: error: not found: type int

       def f3(param1 : String,param2:int=20) = param1+param2

                                     ^

scala> def f3(param1 : String,param2:Int=20) = param1+param2

f3: (param1: String, param2: Int)String

scala> f3("spark")

res3: String = spark20

scala> f3(param2=100,param1="scala")

res4: String = scala100

 sum (1 to 100: _*)

 _*把里面的每个元素提取出来

 scala> def sum(numbers : Int*)={var result =0; for(element <- numbers) result += element;result}

sum: (numbers: Int*)Int

scala> sum(1,2,3,4,5,6,7,8)

res5: Int = 36

scala> sum (1 to 100: _*)

res6: Int = 5050

scala> def morning(content: String) = "Good " + content

morning: (content: String)String

scala> morning("good")

res7: String = Good good

scala> def morning(content: String) {println( "Good " + content)}

morning: (content: String)Unit

scala> morning("luck")

Good luck

scala>

过程就是没有结果，只进行计算

scala> import scala.io.Source._

import scala.io.Source._

scala> lazy val contecnt = fromFile("/root/adsfa")

contecnt: scala.io.BufferedSource = <lazy>

20.懒加载和打印文件

scala>  val contecnt = fromFile("/root/adsfa")

java.io.FileNotFoundException: /root/adsfa (没有那个文件或目录)

    at java.io.FileInputStream.open(Native Method)

    at java.io.FileInputStream.<init>(FileInputStream.java:146)

    at scala.io.Source$.fromFile(Source.scala:90)

    at scala.io.Source$.fromFile(Source.scala:75)

    at scala.io.Source$.fromFile(Source.scala:53)

scala> lazy val contecnt = fromFile("/hadoop/hivedata/a.txt").mkString

contecnt: String = <lazy>

scala> val content = fromFile("/hadoop/hivedata/a.txt").mkString

content: String =

1    w

3    r

5    e

5    v

21.try catch finally

scala> lazy val contecnt = fromFile("/hadoop/hivedata/a.txt").mkString

contecnt: String = <lazy>

scala> val content = fromFile("/hadoop/hivedata/a.txt").mkString

content: String =

1    w

3    r

5    e

5    v

22.array数组

scala> val arr = new Array[Int](5)

arr: Array[Int] = Array(0, 0, 0, 0, 0)

scala> arr(3)

res10: Int = 0

scala> arr(3)=5

scala> arr(3)

res12: Int = 5

scala> arr

res13: Array[Int] = Array(0, 0, 0, 5, 0)

scala> val arr2 = Array("Scala","Spark")

arr2: Array[String] = Array(Scala, Spark)

scala> arr2(1)

res14: String = Spark

scala> arr2(0)

res15: String = Scala

scala> import scala.collection.mutable.Array

ArrayBuffer    ArrayBuilder   ArrayLike      ArrayOps       ArraySeq       ArrayStack     

scala> import scala.collection.mutable.ArrayBu

ArrayBuffer    ArrayBuilder   

scala> import scala.collection.mutable.ArrayBuffer

import scala.collection.mutable.ArrayBuffer

scala> val arrBuffer = ArrayBuffer[Int]()

arrBuffer: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> arrBuffer +=10

res16: arrBuffer.type = ArrayBuffer(10)

scala> arrBuffer

res17: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(10)

scala> arrBuffer +=(2 to 10)

<console>:13: error: type mismatch;

 found   : scala.collection.immutable.Range.Inclusive

 required: Int

              arrBuffer +=(2 to 10)

                             ^

scala> arrBuffer +=(2 to 10 _*)

<console>:13: error: _ must follow method; cannot follow Int(10)

              arrBuffer +=(2 to 10 _*)

                                ^

scala> arrBuffer +=(2,5,6 )

res20: arrBuffer.type = ArrayBuffer(10, 2, 5, 6)

scala> arrBuffer ++= Array(5,6,7)

res21: arrBuffer.type = ArrayBuffer(10, 2, 5, 6, 5, 6, 7)

scala> arrBuffer.trimEnd(7)

scala> arrBuffer

res23: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> arrBuffer

res24: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer()

scala> arrBuffer +=10

res25: arrBuffer.type = ArrayBuffer(10)

scala> arrBuffer +=(5,6,7)

res26: arrBuffer.type = ArrayBuffer(10, 5, 6, 7)

scala> arrBuffer.insert(2,333)

scala> arrBuffer

res28: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(10, 5, 333, 6, 7)

scala> arrBuffer.insert(3,333,555,666,777)

scala> arrBuffer

res30: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(10, 5, 333, 333, 555, 666, 777, 6, 7)

scala>

 scala> arrBuffer.remove(2)

res31: Int = 333

scala> val arr2 = arr

arr         arr2        arrBuffer   

scala> val arr2 = arrBuffer.toArray

arr2: Array[Int] = Array(10, 5, 333, 555, 666, 777, 6, 7)

scala> arr2.toBuffer

res32: scala.collection.mutable.Buffer[Int] = ArrayBuffer(10, 5, 333, 555, 666, 777, 6, 7)

scala> for(elem <- arr2) println(elem)

10

5

333

555

666

777

6

7

scala> for(i <- 1 until(arr2.length,1)) println(arr2(i))

5

333

555

666

777

6

7

scala> for(i <- 1 until(arr2.length,2)) println(arr2(i))

5

555

777

7

scala> arr2.sum

res37: Int = 2359

scala> scala.util.Sorting.quickSort(arr2)

scala> arr2

res40: Array[Int] = Array(5, 6, 7, 10, 333, 555, 666, 777)

scala> arr2.mkString

res41: String = 56710333555666777

scala> arr2.mkString(" ,")

res42: String = 5 ,6 ,7 ,10 ,333 ,555 ,666 ,777

scala> val arr3 = for(i <- arr2) yield i*i

arr3: Array[Int] = Array(25, 36, 49, 100, 110889, 308025, 443556, 603729)

scala> val arr3 = for(i <- arr2 if(i%3 ==0)) yield i*i

arr3: Array[Int] = Array(36, 110889, 308025, 443556, 603729)

scala> arr2.filter{_%3 ==0}map{i =>i*i}

res43: Array[Int] = Array(36, 110889, 308025, 443556, 603729)

23.map

scala> val persons = Map("spark" ->6,"hadoop" -> 11)

persons: scala.collection.immutable.Map[String,Int] = Map(spark -> 6, hadoop -> 11)

scala> persons(spark)

<console>:13: error: not found: value spark

              persons(spark)

                      ^

scala> persons("spark")

res45: Int = 6

scala> val persons = scala.collection.mutable.Map("spark" ->6,"hadoop" -> 11)

persons: scala.collection.mutable.Map[String,Int] = Map(hadoop -> 11, spark -> 6)

scala> persons +=("flink" -> 5)

res47: persons.type = Map(hadoop -> 11, spark -> 6, flink -> 5)

scala> val sparkValue = persons.getOrElse("spark",1000)

sparkValue: Int = 6

scala> for(key <- persons.keySet) println(key +":")

hadoop:

spark:

flink:

scala> val persons =scala.collection.immutable.SortedMap("spark" ->6,"hadoop" -> 11)

persons: scala.collection.immutable.SortedMap[String,Int] = Map(hadoop -> 11, spark -> 6)

scala> persons

res49: scala.collection.immutable.SortedMap[String,Int] = Map(hadoop -> 11, spark -> 6)