Scala中的序列
Scala|顺序
Scala中的序列是一个集合，用于按确定的顺序存储元素。它是索引数据存储区，它允许使用基于0索引的元素的索引来顺序访问其元素。
它是可迭代类的可迭代集合，从中可获取其属性。该返回的有序列表或向量。=在插入顺序被保持。
在Scala中创建序列
首先了解如何在Scala中创建序列。以下语法用于在Scala中创建列表，
语法：
1) Creating an empty sequence,
var emptySeq: Seq[data_type] = Seq();
2) Creating an Sequence with defining the data type,
var mySeq: Seq[data_type] = Seq(element1, element2, ...)
3) Creating an Sequence without defining the data type,
var mySeq = Seq(element1, element2, ...)演示如何在Scala中创建序列的程序
// Program to show how to create a list is Scala
object MyObject {
def main(args: Array[String]) {
// Creating an empty Sequence in Scala
println("Creating an Empty Sequence!")
var empSeq: Seq[Int] = Seq();
println("Empty Sequence : " + empSeq)
// Creating a Sequence by defining its data type
println("\nCreating a Sequence by defining its data type ")
var mySeq: Seq[String] = Seq("Scala", "JavaScript", "Python");
println("Sequence of type 'String': " + mySeq)
// Creating a Sequence without defining its data type
println("\nCreating a Sequence without defining its data type ")
var mySeq2 = Seq(4 ,1 , 6, 7, 2)
println("Sequence without defining its data type: " + mySeq2)
}
}输出：
Creating an Empty Sequence! Empty Sequence : List()Creating a Sequence by defining its data type Sequence of type 'String': List(Scala, JavaScript, Python)Creating a Sequence without defining its data type Sequence without defining its data type: List(4, 1, 6, 7, 2)
Scala中的序列类型
在scala中使用了特征序列的两种类型或子特征。
他们是：
索引序列：索引序列或IndexedSeq返回一个向量，该向量允许对元素的随机和快速访问。
线性序列：线性序列或LinerSeq返回一个List，该List允许快速访问仅第一个和最后一个元素，其余按顺序访问。
程序来说明不同类型的序列
// Program to illustrate different types of Sequence
import scala.collection._
object MyObject {
def main(args: Array[String]) {
// Creating a Indexed Sequence in Scala
val IndSeq = IndexedSeq(3, 6, 9, 12, 15, 18)
println("Indexed Sequence: " + IndSeq)
// Creating a Linear Sequence in Scala
val LinSeq = LinearSeq(2, 4, 6, 8, 10, 12, 14)
println("Linear Sequence: " + LinSeq)
}
}输出：
Indexed Sequence: Vector(3, 6, 9, 12, 15, 18) Linear Sequence: List(2, 4, 6, 8, 10, 12, 14)
常用的序列类型是线性序列。如果仅使用seq关键字初始化序列，则会创建LinerSeq。
Scala序列的操作
Scala中的序列具有许多预定义的功能和要在其上执行的操作。尽管元素不能更改，因为它是不可变的。但是可以执行提取给定索引的元素，查找长度等操作。
程序以给定序列索引访问元素
// Program to access element at a
// given index of the sequence
object MyObject {
def main(args: Array[String]) {
// Creating a Sequence in Scala
val mySeq = Seq(3, 6, 9, 12, 15, 18)
println("Sequence: " + mySeq)
// Access elements at a specific index
println("Element at index 0: " + mySeq(0))
println("Element at index 4: " + mySeq(4))
}
}输出：
Sequence: List(3, 6, 9, 12, 15, 18) Element at index 0: 3 Element at index 4: 15
在Sequence上预定义的常用方法
length：定义序列长度的字段。length：定义序列长度的字段。
语法：
Sequence_name.length
reverse：用于返回新顺序的函数，该顺序为逆序。
语法：
Sequence_name.reverse
isEmpty：用于检查序列是否为空的函数。
语法：
Sequence_name.isEmpty
该程序演示了一些常用的Sequence方法的工作
// Program to access element at a given index of the sequence
object MyObject {
def main(args: Array[String]) {
// Creating a Sequence in Scala
val mySeq = Seq(3, 6, 9, 12, 15, 18)
println("Sequence: " + mySeq)
// Checking if the sequence is empty or not
if(mySeq.isEmpty)
println("\nThe given Sequence is empty")
else
println("\nThe given Sequence is not empty")
// Finding the length of sequence
val len = mySeq.length
println("\nThe length of the seqeunce is " + len)
// Reversing the sequence
val revSeq = mySeq.reverse
println("\nThe reverse of the seqeunce is " + revSeq)
}
}输出：
Sequence: List(3, 6, 9, 12, 15, 18) The given Sequence is not empty The length of the seqeunce is 6 The reverse of the seqeunce is List(18, 15, 12, 9, 6, 3)
Scala为序列定义了更多方法，这些方法将在以后的文章中看到。