linear collections

rockthejvm/scala-3-beginners/src/main/scala/com/rockthejvm/part3fp/LinearCollections.scala

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+package com.rockthejvm.part3fp
+
+object LinearCollections {
+
+  // Seq = well-defined ordering and indexing
+  def testSeq(): Unit = {
+    val aSeq = Seq(1, 2, 3, 4)
+
+    val thirdElement = aSeq.apply(3)
+    // map/flatMap/filter/for
+    val incrementedSeq = aSeq.map(_ + 1)
+    val flatmapped = aSeq.flatMap(x => Seq(x, x + 1))
+    val filtered = aSeq.filter(_ % 2 == 0)
+
+    val reversed = aSeq.reverse
+    val concatenated = aSeq ++ Seq(6, 7, 8)
+    val sorted = aSeq.sorted
+    val sum = aSeq.foldLeft(0)(_ + _)
+    val stringRep = aSeq.mkString
+
+    println(aSeq)
+    println(reversed)
+    println(concatenated)
+    println(sorted)
+    println(sum)
+    println(stringRep)
+  }
+
+  // lists
+  def testLists(): Unit = {
+    val aList = List(1, 2, 3, 4)
+    // same API as Seq
+    val first = aList.head
+    val rest = aList.tail
+    // appending and prepending
+    val aBiggerList = 0 +: aList :+ 4
+    val prepending = 0 :: aList // :: is equivalent to Cons in our LList
+    // utility methods
+    val scalax5 = List.fill(5)("Scala")
+  }
+
+  // ranges
+  def testRanges(): Unit = {
+    val aRange: Seq[Int] = 1 to 10 // inclusive
+    val nonInclusive: Seq[Int] = 1 until 10 // non-inclusive
+    // same Seq API
+    (1 to 10).foreach(println)
+  }
+
+  // arrays
+  def testArray(): Unit = {
+    val anArray = Array(1, 2, 3, 4) // int[] on the JVM
+    // has access most Seq API
+    // Arrays are not Seqs
+    val aSeq: Seq[Int] = anArray.toIndexedSeq
+
+    // arrays are mutable
+    anArray.update(1, 99)
+
+    println(anArray.mkString("Array(", ", ", ")"))
+  }
+
+  // vectors = fast sequences for a large amount of data
+  def testVector(): Unit = {
+    val aVector = Vector(1, 2, 3, 4, 5)
+    // the same Seq API
+  }
+
+  // set - no duplicates
+  def testSets(): Unit = {
+    val aSet = Set(1, 2, 3, 4, 5)
+    // equals + hashcode = hash set
+    // main API test if in set
+    val contains3 = aSet.contains(3)
+    val contains3_v2 = aSet.apply(3)
+
+    println(contains3)
+
+    // adding/removing
+    val aBiggerSet = aSet + 44
+    val anotherSet = aSet - 4
+    println(aBiggerSet.mkString(","))
+    println(anotherSet.mkString(","))
+    println((aBiggerSet ++ anotherSet).mkString(","))
+    println((aBiggerSet union anotherSet).mkString(","))
+    println((aBiggerSet | anotherSet).mkString(",")) // '&' alias for union
+
+    // difference
+    val aDiffSet = aSet.diff(anotherSet)
+    val aDiffSet_v2 = aSet -- anotherSet
+
+    // intersection
+    val aIntersectSet = aSet.intersect(anotherSet)
+    val aIntersectSet_v2 = aSet & anotherSet
+  }
+
+  def main(args: Array[String]): Unit = {
+    testSeq()
+    testRanges()
+    testArray()
+    testSets()
+  }
+}