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。。。。。