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📜  Scala Seq

📅  最后修改于: 2021-01-09 12:08:41             🧑  作者: Mango

Scala Seq

Seq是一个特征，代表可以保证不变的索引序列。您可以使用元素索引来访问元素。它保持元素的插入顺序。

序列支持多种方法来查找元素或子序列的出现。它返回一个列表。

Scala Seq示例

在以下示例中，我们将创建Seq并从Seq访问元素。

import scala.collection.immutable._
object MainObject{
    def main(args:Array[String]){
        var seq:Seq[Int] = Seq(52,85,1,8,3,2,7)
        seq.foreach((element:Int) => print(element+" "))
        println("\nAccessing element by using index")
        println(seq(2))
    }
}

输出：

52 85 1 8 3 2 7 
Accessing element by using index
1

您还可以使用反向方法以相反的顺序访问元素。下面我们列出了一些常用的方法及其说明。

常用的Seq方法

Method Description
def contains[A1 >: A](elem: A1): Boolean Check whether the given element present in this sequence.
def copyToArray(xs: Array[A], start: Int, len: Int): Unit It copies the seq elements to an array.
def endsWith[B](that: GenSeq[B]): Boolean It tests whether this sequence ends with the given sequence or not.
def head: A It selects the first element of this seq collection.
def indexOf(elem: A): Int It finds index of first occurrence of a value in this immutable sequence.
def isEmpty: Boolean It tests whether this sequence is empty or not.
def lastIndexOf(elem: A): Int It finds index of last occurrence of a value in this immutable sequence.
def reverse: Seq[A] It returns new sequence with elements in reversed order.

Scala Seq示例

在此示例中，我们应用了一些预定义的Seq特征方法。

import scala.collection.immutable._
object MainObject{
    def main(args:Array[String]){
        var seq:Seq[Int] = Seq(52,85,1,8,3,2,7)
        seq.foreach((element:Int) => print(element+" "))
        println("\nis Empty: "+seq.isEmpty)
        println("Ends with (2,7): "+ seq.endsWith(Seq(2,7)))
        println("contains 8: "+ seq.contains(8))
        println("last index of 3 : "+seq.lastIndexOf(3))
        println("Reverse order of sequence: "+seq.reverse)
    }
}

输出：

52 85 1 8 3 2 7 
is Empty: false
Ends with (2,7): true
contains 8: true
last index of 3 : 4
Reverse order of sequence: List(7, 2, 3, 8, 1, 85, 52)