Scala 中的 ListSet

集合是仅包含不可重复的唯一项目的集合，列表是包含不可变数据的集合。在 Scala 中， ListSet class使用基于列表的数据结构实现不可变集合。元素以相反的插入顺序存储，这意味着最新的元素位于列表的头部。它维护插入顺序。

Listset 仅用于少数元素。我们可以通过调用构造函数或应用函数ListSet.empty 。它的迭代和遍历方法以它们首次插入的相同顺序访问元素。

句法：

var ListSetName = ListSet(element1, element2, element3, ....)  

ListSet 操作

初始化 ListSet ：下面是创建或初始化 ListSet 的示例。

// Scala program to Initialize a ListSet 
import scala.collection.immutable._
  
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        println("Initializing an immutable ListSet ")
          
        // Creating ListSet
        val listSet1: ListSet[String] = ListSet("GeeksForGeeks",
                                            "Article", "Scala")
        println(s"Elements of listSet1 = $listSet1")
    } 
} 

输出：

Initializing an immutable ListSet 
Elements of listSet1 = ListSet(Scala, Article, GeeksForGeeks)

检查 ListSet 中的特定元素：

// Scala program to Check specific elements in ListSet 
import scala.collection.immutable._
  
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        println("Initializing an immutable ListSet ")
          
        // Creating ListSet
        val listSet1: ListSet[String] = ListSet("GeeksForGeeks",
                                            "Article", "Scala")
        println(s"Elements of listSet1 = $listSet1")
          
        println("Check elements of immutable ListSet")
          
        // Checking element in a ListSet
        println(s"GeeksForGeeks = ${listSet1("GeeksForGeeks")}")
        println(s"Student = ${listSet1("Student")}")
        println(s"Scala = ${listSet1("Scala")}")
    } 
} 

输出：

Initializing an immutable ListSet 
Elements of listSet1 = ListSet(Scala, Article, GeeksForGeeks)
Check elements of immutable ListSet
GeeksForGeeks = true
Student = false
Scala = true

在 ListSet 中添加元素：我们可以使用 +运算符在 ListSet 中添加元素。下面是在 ListSet 中添加元素的示例。

// Scala program to Add an element in a ListSet
import scala.collection.immutable._
  
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        println("Initializing an immutable ListSet ")
          
        // Creating ListSet
        val listSet1: ListSet[String] = ListSet("GeeksForGeeks",
                                            "Article", "Scala")
        println(s"Elements of listSet1 = $listSet1")
          
        // Adding element in ListSet
        println("Add element of immutable ListSet ")
        val listSet2: ListSet[String] = listSet1 + "Java"
        println(s"Adding element java to ListSet $listSet2")
    } 
} 

输出：

Initializing an immutable ListSet 
Elements of listSet1 = ListSet(Scala, Article, GeeksForGeeks)
Add element of immutable ListSet 
Adding element java to ListSet ListSet(Java, Scala, Article, GeeksForGeeks)

添加两个ListSet：我们可以使用++运算符添加两个ListSet。下面是添加两个 ListSet 的示例。

// Scala program to Add two ListSet
import scala.collection.immutable._
  
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        println("Initializing an immutable ListSet ")
          
        // Creating ListSet
        val listSet1: ListSet[String] = ListSet("GeeksForGeeks",
                                               "Article", "Scala")
        println(s"Elements of listSet1 = $listSet1")
          
        // Adding two ListSet
        val listSet2: ListSet[String] = listSet1 ++ ListSet("Java", 
                                                            "Csharp")
        println(s"After adding two lists $listSet2")
          
  
    } 
} 

输出：

Initializing an immutable ListSet 
Elements of listSet1 = ListSet(Scala, Article, GeeksForGeeks)
After adding two lists ListSet(Java, Csharp, Scala, Article, GeeksForGeeks)

从 ListSet 中删除元素：我们可以使用 –运算符删除 ListSet 中的元素。下面是在 ListSet 中删除元素的示例。

// Scala program to Remove element from the ListSet
import scala.collection.immutable._
  
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        println("Initializing an immutable ListSet ")
          
        // Creating ListSet
        val listSet1: ListSet[String] = ListSet("GeeksForGeeks",
                                                "Article", "Scala")
        println(s"Elements of listSet1 = $listSet1")
          
        println("Remove element from the ListSet ")
        val listSet2: ListSet[String] = listSet1 - ("Article")
        println(s"After removing element from listset = $listSet2")
          
  
    } 
} 

输出：

Initializing an immutable ListSet 
Elements of listSet1 = ListSet(Scala, Article, GeeksForGeeks)
Remove element from the ListSet 
After removing element from listset = ListSet(Scala, GeeksForGeeks)

初始化一个空的 ListSet ：

// Scala program to print empty ListSet
import scala.collection.immutable._
  
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        // Creating an empty ListSet
        println("Initialize an empty ListSet")
        val emptyListSet: ListSet[String] = ListSet.empty[String]
        println(s"String type empty ListSet = $emptyListSet")
          
    } 
} 

输出：

Initialize an empty ListSet
String type empty ListSet = ListSet()

注意：我们可以通过应用函数ListSet.empty或调用构造函数来创建空 ListSet。