Spark学习使用笔记 - Scala篇（1）

基础

 def primitiveType(): Unit = {    //scala没有原始类型，都是对象    println("1.toString -> " + 1.toString)    //富类型自动转换Int->RichInt再调用to    println("1.to(199) -> " + 1.to(199))    println("\"Hello.intersect(\"low\")\" -> " + "Hello".intersect("low"))    //a.方法(b)  ==  a 方法 b    println("1.to(199) -> " + (1 to 199))    //scala没有++或者--  }  def callFunction = {    println("sqrt(2) -> " + sqrt(2))    println("pow(2,4) -> " + pow(2, 4))    println("min(3,Pi)" + min(3, Pi))    println("\"jsjsjdaj\".distinct -> " + "jsjsjdaj".distinct)  }  def applyMethod: Unit = {    //字符串字符定位    println("\"hello\"(4) -> " + "hello" (4))    println("\"hello\".apply(4) -> " + "hello".apply(4))    //构建对象常用方法    println("BigInt(\"12344567890\") -> " + BigInt("1234567890"))    println("Array(1,2,3,4,5,6,7,8,9,0) -> " + Array(1, 2, 3, 4, 5, 6, 7, 8, 9, 0))  }  def exercise: Unit = {    println(pow(sqrt(3.0), 2.0))    println("\"asdasd\" * 3 -> " + ("asdasd" * 3))    println("10 max 2 -> " + (10 max 2))    println("BigInt(\"2\") pow 1024 -> " + (BigInt("2") pow 1024))    println("probablePrime(10, Random) -> " + probablePrime(10, Random))    println("随机文件名：" + BigInt(Random.nextInt()).toString(36))    val str = "abcdefghijklmn"    println("str(0) -> " + str(0))    println("str.take(0) -> " + str.take(1))    println("str.reverse(0) -> " + str.reverse(0))    println("str.takeRight(0) -> " + str.takeRight(1))  }

输出：

1.toString -> 11.to(199) -> Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199)"Hello.intersect("low")" -> lo1.to(199) -> Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199)sqrt(2) -> 1.4142135623730951pow(2,4) -> 16.0min(3,Pi)3.0"jsjsjdaj".distinct -> jsda"hello"(4) -> o"hello".apply(4) -> oBigInt("12344567890") -> 1234567890Array(1,2,3,4,5,6,7,8,9,0) -> [I@2bc7c6c32.9999999999999996"asdasd" * 3 -> asdasdasdasdasdasd10 max 2 -> 10BigInt("2") pow 1024 -> 179769313486231590772930519078902473361797697894230657273430081157732675805500963132708477322407536021120113879871393357658789768814416622492847430639474124377767893424865485276302219601246094119453082952085005768838150682342462881473913110540827237163350510684586298239947245938479716304835356329624224137216probablePrime(10, Random) -> 811随机文件名：aa52hjstr(0) -> astr.take(0) -> astr.reverse(0) -> nstr.takeRight(0) -> n

控制结构和函数

{}块是有值的，值就是最后一个表达式的值;没有值的表达式（比如说赋值类型的）值为Unit

def value = {    val a = {      val b = 1      b    }    println("a->" + a)    var d = 0    val c = d = 1;    println("c -> " + c)  }

输出：

a->1c -> ()

条件表表达式有值，值就是各个分支，缺少分支为Unit，完整分支为所有分支类型

   def conditionExpression: Unit = {    val cond = 1    val a =      if (cond == 1)        true      else        false    println(a)  }  def conditionType: Unit = {    val cond = 1    var a = //Unit类型      if (cond == 0)        1    //上面的相当于    a =      if (cond == 0)        1      else        ()    val b = //Any类型      if (cond == 2)        1      else        "hello"    println("a -> " + a)    println("b -> " + b)  }

输出：

truea -> ()b -> hello

scala没有受检异常，throw表达式类型为Nothing

def handleException: Unit = {    //scala没有受检异常    //throw表达式类型为Nothing    println("---------------------------------------------")    val cond = 1    try {      val a =        if (cond == 0)          true        else if (cond < 0)          throw new IllegalArgumentException("cond is less than 0!")        else          throw new Exception("cond is larger than 0!")    } catch {      case e1: IllegalArgumentException => e1.printStackTrace()      case e2: Exception => e2.printStackTrace()    } finally {      println("finally block!")    }    //对于条件分支，如果一个分支返回throw表达式，那么它的类型就是其他分支的类型  }

输出：

---------------------------------------------java.lang.Exception: cond is larger than 0!    at com.hash.learn.scala.Chapter2.exception$.handleException(exception.scala:21)    at com.hash.learn.scala.Chapter2.CMain$.main(CMain.scala:25)    at com.hash.learn.scala.Chapter2.CMain.main(CMain.scala)    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)    at java.lang.reflect.Method.invoke(Method.java:606)    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)finally block!

参数

  def parameter: Unit = {    //带名参数    def decorate(left: String = "[", middle: String, right: String = "]") = left + middle + right    println(decorate(middle = "asd"))    //匿名参数    def decorate2(middle: String, left: String = "[", right: String = "]") = left + middle + right    println(decorate2("asd"))    //变长参数(输入为Seq)    def sum(args: Int*) = {      var sum = 0      for (i <- args) {        sum += i      }      sum    }    println(sum(1, 9, 9, 9))    //Range to Seq    println(sum(1 to 9: _*))  }

输出：

[asd][asd]2845

循环

def whileLoop: Unit = {    var n = 10    while (n > 0) {      println(n)      n -= 1    }  }  def forLoop: Unit = {    //to 为闭区间    for (i <- 1 to 5)      println(i)    //until为左闭右开区间    for (i <- 1 until 5)      println(i)    println("---------------------------------------------")    //可以用字符串    for (i <- "abcdefg")      println(i)  }  def advanceForLoop: Unit = {    //嵌套循环写在同一行    println("---------------------------------------------")    for (i <- 1 to 3; j <- 1 to 3)      println("i:" + i + " j:" + j)    //可以加条件    println("---------------------------------------------")    for (i <- 1 to 3; j <- 1 to 3 if i != j)      println("i:" + i + " j:" + j)    //可以有中间变量    println("---------------------------------------------")    for (i <- 1 to 10; from = i % 3; j <- 1 to from)      println("i:" + i + " j:" + j)    //for推导式    println(for (i <- 1 to 10) yield i)    println(for (i <- 1 to 10) yield i % 3)    //推导式生成的集合类型和第一个生成器类型兼容    println(for (i <- "abcdefg"; j <- 1 to 2) yield i)    println(for (j <- 1 to 2; i <- "abcdefg") yield i)  }

输出：

10987654321123451234---------------------------------------------abcdefg---------------------------------------------i:1 j:1i:1 j:2i:1 j:3i:2 j:1i:2 j:2i:2 j:3i:3 j:1i:3 j:2i:3 j:3---------------------------------------------i:1 j:2i:1 j:3i:2 j:1i:2 j:3i:3 j:1i:3 j:2---------------------------------------------i:1 j:1i:2 j:1i:2 j:2i:4 j:1i:5 j:1i:5 j:2i:7 j:1i:8 j:1i:8 j:2i:10 j:1Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)Vector(1, 2, 0, 1, 2, 0, 1, 2, 0, 1)aabbccddeeffggVector(a, b, c, d, e, f, g, a, b, c, d, e, f, g)