设置在 Scala |第 2 组
先决条件：在 Scala 中设置 |第一组
在Set中，我们只能在可变集合中添加新元素。 +=, ++==和
add()方法用于在可变集合中使用可变集合时添加新元素，而 += 用于在不可变集合中使用可变集合时添加新元素。示例 1：
// Scala program to illustrate how to
// add items using +=, ++== and add()
// method in mutable set with mutable
// collection
import scala.collection.mutable._
object Main
{
def main(args: Array[String])
{
// Creating and initilazing set
var myset = Set("G", "Geek", "for")
println("Set before addition "+
"of new elements:")
println(myset)
// Adding new element in set
// using += and ++==
myset += "Geeks"
// Here, "G" is already present in the
// Set so, "G" is not added in set
myset ++== List("Geeks12", "geek23", "G")
// Adding elements using add() method
myset.add("GeeksforGeeks")
myset.add("geeksForgeeks100")
println("\nSet after addition of new elements:")
println(myset)
}
}
输出：
Set before addition of new elements:
Set(for, G, Geek)
Set after addition of new elements:
Set(geek23, for, Geeks, G, Geek, Geeks12, geeksForgeeks100, GeeksforGeeks)
示例 2：
// Scala program to illustrate how
// to add items using += operator in
// mutable set with immutable collection
import scala.collection.immutable._
object Main
{
def main(args: Array[String])
{
// Creating and initializing mutable set
var myset = Set("G", "Geek", "for")
println("Set before addition" +
" of new elements:")
println(myset)
// Adding new element in set
// using += operator
myset += "GeeksforGeeks"
myset += "geeks1000"
println("\nSet after addition " +
"of new elements:")
println(myset)
}
}
输出：
Set before addition of new elements:
Set(G, Geek, for)
Set after addition of new elements:
Set(for, Geek, G, geeks1000, GeeksforGeeks)
在 Set 中，我们只能移除可变集合中的元素。 -=和–=方法用于删除元素，当我们使用可变集合中的可变集合时，我们还可以使用
retain() 、 clear()和remove()方法来删除元素。 -=运算符用于在不可变集合中使用可变集合时删除元素。示例 1：
// Scala program to illustrate
// how to delete items using -=
// and --= methods in mutalbe set
// with mutable collection
import scala.collection.mutable._
object Main
{
def main(args: Array[String])
{
// Creating and initilazing
//mutable set
var myset = Set(100, 400, 500,
600, 300, 800)
println("Set before deletion:")
println(myset)
// Deleting elements in set
// using -= and --= methods
myset -= 600
myset --= List(300, 100)
println("\nSet after deletion:")
println(myset)
}
}
输出：
Set before deletion:
Set(300, 100, 800, 500, 600, 400)
Set after deletion:
Set(800, 500, 400)
示例 2：
// Scala program to illustrate
// how to delete items using
// retain(), and clear() methods
// in mutalbe set with mutable
// collection
import scala.collection.mutable._
object Main
{
def main(args: Array[String])
{
// Creating and initializing
// mutable set
var myset1 = Set(100, 400, 500,
600,300, 800)
var myset2 = Set(11, 44, 55, 66, 77)
println("Set before deletion:")
println(myset1)
println(myset2)
// Deleting elements in set
// using retain() method
myset1.retain(_>500)
println("\nSet after using retain()" +
" method:")
println(myset1)
// Deleting elements in set
// using clear() method
myset2. clear
println("\nSet after using clear() method:")
println(myset2)
}
}
输出：
Set before deletion:
Set(300, 100, 800, 500, 600, 400)
Set(66, 55, 11, 44, 77)
Set after using retain() method:
Set(800, 600)
Set after using clear() method:
Set()
在不可变集合中，我们不能添加元素，但我们可以使用+和++运算符从不可变集合中添加元素并将结果存储到新变量中。这里，+ 用于添加单个或多个元素，++ 用于添加在另一个序列中定义的多个元素以及不可变集合的串联。
例子：
// Scala program to illustrate how
// to add elements in immutable set
import scala.collection.immutable._
object Main
{
def main(args: Array[String])
{
// Creating and initilazing
// immutable set
val myset1 = Set(100, 400, 500,
600,300, 800)
val myset2 = Set(11, 44, 55, 66, 77)
println("Set before addition:")
println(myset1)
println(myset2)
println("\nSet after addition:")
// Add single element in myset1
// and create new Set
val S1 = myset1 + 900
println(S1)
// Add multiple elements in myset1
// and create new Set
val S2 = myset1 + (200, 300)
println(S2)
// Add another list into myset1
// and create new Set
val S3 = myset1 ++ List(700, 1000)
println(S3)
// Add another set myset2 into
// myset1 and create new Set
val S4 = myset1 ++ myset2
println(S4)
}
}
输出：
Set before addition:
Set(500, 600, 800, 300, 400, 100)
Set(77, 44, 66, 11, 55)
Set after addition:
Set(500, 900, 600, 800, 300, 400, 100)
Set(500, 600, 800, 300, 400, 200, 100)
Set(500, 700, 1000, 600, 800, 300, 400, 100)
Set(500, 77, 44, 66, 600, 11, 55, 800, 300, 400, 100)
在immutable set中，我们不能移除元素，但我们可以使用–和–运算符从不可变集合中移除元素并将结果存储到新变量中。这里，-运算符用于删除一个或多个元素，-运算符用于删除另一个序列中定义的多个元素。
例子：
// Scala program to illustrate how
// to remove elements in immutable set
import scala.collection.immutable._
object Main
{
def main(args: Array[String])
{
// Creating and initilazing
// immutable set
val myset = Set(100, 400, 500, 600,
300, 800, 900, 700)
println("Set before deletion:")
println(myset)
println("\nSet after deletion:")
// Remove single element in myset and
// Result store into new variable
val S1 = myset - 100
println(S1)
// Remove multiple elements from myset
// Result store into new variable
val S2 = myset - (400, 300)
println(S2)
// Remove another list from myset
// Result store into new variable
val S3 = myset -- List(700, 500)
println(S3)
}
}
输出：
Set before deletion:
Set(500, 900, 700, 600, 800, 300, 400, 100)
Set after deletion:
Set(500, 900, 700, 600, 800, 300, 400)
Set(500, 900, 700, 600, 800, 100)
Set(900, 600, 800, 300, 400, 100)
现在我们将看到一些关于集合的基本数学运算，例如并集、交集和差集。
- Union：在这种情况下，我们可以简单地将一个 Set 与另一个相加。由于 Set 本身不允许任何重复条目，因此我们不需要处理公共值。要执行联合，我们使用 union() 方法。
- 交集：为了从两个集合中获取公共值，我们使用 intersect() 方法。它返回一个新集合，其中包含两个集合中存在的所有公共值。
- 差异：为了获得两个集合的差异，我们使用 diff() 方法。它返回包含 myset2 中不存在的所有内容的集合。
例子：
// Scala program to illustrate union,
// intersection, and difference on Set
import scala.collection.immutable._
object Main
{
def main(args: Array[String])
{
// Creating and initializing set
val myset1 = Set(11, 22, 33, 44,
55, 66, 77, 111)
val myset2 = Set(88, 22, 99, 44,
55, 66, 77)
// To find intersection
val S1 = myset1.intersect(myset2)
println("Intersection:")
println(S1)
// To find the symmetric difference
val S2 = myset1.diff(myset2)
println("\nDifference:")
println(S2)
// To find union
val S3 = myset1.union(myset2)
println("\nUnion:")
println(S3)
}
}
输出：
Intersection:
Set(77, 22, 44, 66, 55)
Difference:
Set(33, 11, 111)
Union:
Set(88, 33, 77, 22, 44, 66, 11, 99, 55, 111)