大数据系列修炼-Scala课程02
Scala数组操作实战详解
接着昨天的课程，下面我们继续学习关于Scala数组操作详解。
Scala数组的定义
//数组定义 //定长数组格式 /** * val arrayName = new Array[datatype](length) * val arrayName = Array(constant1,constant2,....) */ //不定长数组定义格式 /* * var arrayBufferName =ArrayBuffer[datatype]() */
数组的基本操作：包括截取(trimEnd)，插入(insert)，移除(remove)，转换(toArray)等函数，居然发现eclipse开发工具中有一个很好的调试工具能够查看更多的变量值Scala Worksheet 非常好用！希望大家用用！
val b =ArrayBuffer[Int]() //> b : scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer() b += 5 //> res0: com.dt.zhangsh.scala.ArrrayOp.b.type = ArrayBuffer(5) b //> res1: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5) b += (1,2,78,2) //> res2: com.dt.zhangsh.scala.ArrrayOp.b.type = ArrayBuffer(5, 1, 2, 78, 2) b ++= Array(45,2,1) //> res3: com.dt.zhangsh.scala.ArrrayOp.b.type = ArrayBuffer(5, 1, 2, 78, 2, 45, //| 2, 1) b.trimEnd(5) b //> res4: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5, 1, 2) b.insert(2, 6) b //> res5: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5, 1, 6, 2) b.insert(2, 7, 8, 9) b //> res6: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5, 1, 7, 8, 9, //| 6, 2) b.remove(2) //> res7: Int = 7 b //> res8: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5, 1, 8, 9, 6, //| 2) b.remove(2, 3) b //> res9: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(5, 1, 2) b.toArray //> res10: Array[Int] = Array(5, 1, 2)
数组的进阶操作：进阶包括：求倍数(map)、求和(sum)、最大值(max)、排序(sorted)、快速排序(quickSort)、拼接(mkString)等函数
//数组进阶 val c = Array(2, 3, 5, 7, 11) //> c : Array[Int] = Array(2, 3, 5, 7, 11) //数组乘以5 必须包含yield 用于结果输出 val result = for (elem <- c) yield 5 * elem //> result : Array[Int] = Array(10, 15, 25, 35, 55) result //> res11: Array[Int] = Array(10, 15, 25, 35, 55) // for (elem <- c if elem % 2 == 0) yield 2 * elem //> res12: Array[Int] = Array(4) //_为占位符 如果能被2余数为0的数据放到map中并且乘以2 c.filter(_ % 2 == 0).map(2 * _) //> res13: Array[Int] = Array(4) c //> res14: Array[Int] = Array(2, 3, 5, 7, 11) //求和 Array(1, 7, 2, 9).sum //> res15: Int = 19 //字符串最长 ArrayBuffer("Mary", "had", "a", "little", "lamb").max //> res16: String = little val d = ArrayBuffer(1, 7, 2, 9) //> d : scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 7, 2, 9) //排序 val bSorted = d.sorted //> bSorted : scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 7, //| 9) val e = Array(1, 7, 2, 9) //> e : Array[Int] = Array(1, 7, 2, 9) //快速排序 scala.util.Sorting.quickSort(e) e //> res17: Array[Int] = Array(1, 2, 7, 9) //拼接 e.mkString(" and ") //> res18: String = 1 and 2 and 7 and 9 e.mkString("<", ",", ">") //> res19: String = <1,2,7,9>
多维数组定义：在一维数组的基础添加多维数组，数组中包含数组
//多维数组 //数组中添加一维数组 val matrix = Array.ofDim[Double](3, 4) //> matrix : Array[Array[Double]] = Array(Array(0.0, 0.0, 0.0, 0.0), Array(0.0 //| , 0.0, 0.0, 0.0), Array(0.0, 0.0, 0.0, 0.0)) matrix(2)(1) = 110 matrix //> res20: Array[Array[Double]] = Array(Array(0.0, 0.0, 0.0, 0.0), Array(0.0, 0 //| .0, 0.0, 0.0), Array(0.0, 110.0, 0.0, 0.0)) val triangle = new Array[Array[Int]](10) //> triangle : Array[Array[Int]] = Array(null, null, null, null, null, null, n //| ull, null, null, null) for (i <- 0 until triangle.length) triangle(i) = new Array[Int](i + 1) triangle //> res21: Array[Array[Int]] = Array(Array(0), Array(0, 0), Array(0, 0, 0), Arr //| ay(0, 0, 0, 0), Array(0, 0, 0, 0, 0), Array(0, 0, 0, 0, 0, 0), Array(0, 0, //| 0, 0, 0, 0, 0), Array(0, 0, 0, 0, 0, 0, 0, 0), Array(0, 0, 0, 0, 0, 0, 0, 0 //| , 0), Array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
Map、Tuple、Zip实战解析
Map实战：主要包括Map不可变(immutable)、Map可变(mutable)、getOrElse方法、map的真删改、排序等
//map 不可变 val map = Map("book"->10,"gun"->18,"ipad"->1000)//> map : scala.collection.immutable.Map[String,Int] = Map(book -> 10, gun -> 1 //| 8, ipad -> 1000) for((k,v) <- map) yield (k,v * 0.9) //> res0: scala.collection.immutable.Map[String,Double] = Map(book -> 9.0, gun - //| > 16.2, ipad -> 900.0) //Map 可变 val scores = scala.collection.mutable.Map("Scala" -> 7, "Hadoop" -> 8, "Spark" -> 10 ) //> scores : scala.collection.mutable.Map[String,Int] = Map(Hadoop -> 8, Spark //| -> 10, Scala -> 7) //Map中getOrElse方法判断是否有key，如果flase就为后面value val hadoopScore = scores.getOrElse("Hadoop", 0) //> hadoopScore : Int = 8 //向Map中添加数值 scores += ("R" -> 9) //> res1: com.dt.zhangsh.scala.ScalaOpWorkSheet.scores.type = Map(Hadoop -> 8, R //| -> 9, Spark -> 10, Scala -> 7) //删除 scores -= "Hadoop" //> res2: com.dt.zhangsh.scala.ScalaOpWorkSheet.scores.type = Map(R -> 9, Spark //| -> 10, Scala -> 7) //排序 val sortedScore = scala.collection.immutable.SortedMap("Scala" -> 7, "Hadoop" -> 8, "Spark" -> 10 ) //> sortedScore : scala.collection.immutable.SortedMap[String,Int] = Map(Hadoop //| -> 8, Scala -> 7, Spark -> 10)
Tuple实战：tuple最主要是自动识别变量类型，遍历时从1开始，可以用空格或者点加占位符进行数据访问，截取大写字母后拼接以及获得tuple中的部分数据，不需要的用占位符代替
//tuple主要是能够自动识别变量类型，自己查看类型 val tuple =(1,2,3.14,"Rocky","Spark") //> tuple : (Int, Int, Double, String, String) = (1,2,3.14,Rocky,Spark) //遍历时从1开始,可以是空格或者加占位符序列进行访问 val third = tuple._3 //> third : Double = 3.14 //可以把tuple给一变量，如果只需一部分，其他的用占位符代替 val (first,second,thirda,fourth,fifth) = tuple //> first : Int = 1 //| second : Int = 2 //| thirda : Double = 3.14 //| fourth : String = Rocky //| fifth : String = Spark val (f, s, _, _, _) = tuple //> f : Int = 1 //| s : Int = 2 //截取大写字母后拼接 "Scala Spark".partition(_.isUpper) //> res3: (String, String) = (SS,cala park)
Zip操作实战：按照两个数组的序列进行匹配组成心得元素
//Zip实战：包括按照序列进行匹配为元素 val symbols = Array("[", "-", "]") //> symbols : Array[String] = Array([, -, ]) val counts = Array(2,5,2) //> counts : Array[Int] = Array(2, 5, 2) val pairs = symbols.zip(counts) //> pairs : Array[(String, Int)] = Array(([,2), (-,5), (],2)) for ((x,y) <- pairs) println(x*y) //> [[ //| ----- //| ]]
Scala类的属性和对象私有字段实战详解
Scala类的使用实战：Scala类中变量必须赋值并且方法变量的时候用的还方法访问(def b_)
getter与setter实战:getter与setter方法只有是普通变量就行了
对象私有属性实战：使用private修饰的变量可以getter，没有setter，private[this]只能在本类中使用
class People { //定义的变量 必须赋值，只有不为private变量，它就用于setter和getter方法 var age =0 def increment() {age +=1} def current = age } class Student{ //私有的变量只有getter方法没有setter方法 private var privateAge = 0 //private[this]修饰的变量只能当前类使用 private[this] val name = "Scala" def age = privateAge def isYounger(other: Student) = privateAge < other.privateAge } object HelloOOP{ def main(args: Array[String]): Unit = { val people=new People people.age =10 // people.increment() // people.increment() // println(people.current) // // val student = new Student // //student.age=10//私有的不能设置值 // println(student.age) // val student = new Student // println(student.name) } }
Scala主构造器、私有构造器、构造器重载实战详解
Scala主构造器实战：Scala类中可以添加参数的，主构造器就是默认的构造器
私有构造器实战 :主构造器重构必须集成主构造器！
构造器重载实战:如果Scala类是私有的，者不能被实例化，只有重构构造器才能使用
object ScalaOOP { def main(args: Array[String]): Unit = { // val p = new Teacher // p.name = "Spark" // // p.sayHello // val p = new Teacher("Spark", 5) // println(" : " + p.age) val p = new Teacher("Spark", 5 , "male") println(" : " + p.age) } } //class Teacher { // var name : String = _ // private var age = 27 // private[this] val gender = "male" // // def this(name:String){ // this // this.name = name // } // // def sayHello(){ // println(this.name + ":" + this.age + " : " + this.gender) // } //} //如果Scala类是私有的，者不能被实例化，只有重构构造器才能使用 class Teacher private (val name : String, val age : Int){ println("This is the primary constructor!!!") var gender : String = _ println(gender) def this(name : String, age : Int, gender : String){ this(name, age) this.gender = gender } }
未完待续。。。。。
