SCALA-706: Code companion for the article (#1413)

* SCALA-706: Code companion for the article

* SCALA-706: Code companion for the article

Author: oforero

build.sbt

@@ -143,6 +143,15 @@ lazy val scala_core_oop = (project in file("scala-core-modules/scala-core-oop"))
       Seq(catsEffect, jUnitInterface) ++ scalaTestDeps
   )
 
+lazy val scala_strings_2 = (project in file("scala-core-modules/scala-strings-2"))
+  .settings(
+    name := "scala-core-strings",
+    libraryDependencies ++= scalaTestDeps,
+    libraryDependencies += jUnitInterface,
+    scalaVersion := scala3Version
+  )
+
+
 lazy val scala_core_fp = (project in file("scala-core-modules/scala-core-fp"))
   .settings(
     name := "scala-core-fp",

scala-core-modules/scala-strings-2/README.md

@@ -0,0 +1,6 @@
+## Core Scala Strings
+
+This module contains articles about Scala's Strings.
+
+### Relevant Articles:
+

scala-core-modules/scala-strings-2/src/main/scala/com/baeldung/scala/strings/checkempty/EmptyPatternMatchingExtensions.scala

@@ -0,0 +1,25 @@
+package com.baeldung.scala.strings.checkempty
+
+object EmptyPatternMatchingExtensions {
+  extension (seq: Seq[?])
+    def isNullOrEmpty: Boolean = seq match {
+      case null  => true
+      case Seq() => true
+      case s     => false
+    }
+
+  extension (seq: Seq[Char])
+    def isNullOrEmptyOrWhitespace: Boolean = seq match {
+      case null  => true
+      case Seq() => true
+      case s     => s.forall(_.isWhitespace)
+    }
+
+  extension (str: String)
+    def isNullOrEmptyOrWhitespace: Boolean = str match {
+      case null => true
+      case ""   => true
+      case s    => s.trim.isEmpty
+    }
+
+}

scala-core-modules/scala-strings-2/src/main/scala/com/baeldung/scala/strings/checkempty/EmptySeqExtensions.scala

@@ -0,0 +1,10 @@
+package com.baeldung.scala.strings.checkempty
+
+object EmptySeqExtensions {
+  extension (objs: Seq[?])
+    def isNullOrEmpty: Boolean = objs == null || objs.isEmpty
+
+  extension (objs: Seq[Char])
+    def isNullOrEmptyOrWhitespace: Boolean =
+      objs.isNullOrEmpty || objs.forall(_.isWhitespace)
+}

scala-core-modules/scala-strings-2/src/main/scala/com/baeldung/scala/strings/checkempty/EmptyStringExtensions.scala

@@ -0,0 +1,8 @@
+package com.baeldung.scala.strings.checkempty
+
+object EmptyStringExtensions {
+  extension (str: String)
+    def isEmptyOrWhitespace: Boolean = str.trim.isEmpty
+    def isNullOrEmptyOrWhitespace: Boolean =
+      str == null || str.isEmptyOrWhitespace
+}

scala-core-modules/scala-strings-2/src/main/scala/com/baeldung/scala/strings/checkempty/VerifiedStringExtensions.scala

@@ -0,0 +1,22 @@
+package com.baeldung.scala.strings.checkempty
+
+type Empty
+type NonEmpty
+
+opaque type VerifiedString[T] = String
+
+object VerifiedString:
+  def apply[T](value: String): VerifiedString[T] = value
+
+  given Conversion[VerifiedString[NonEmpty], String] = _.value
+
+  extension (str: String)
+    def asVerifiedString =
+      if str.isNullOrEmptyOrWhitespace then VerifiedString[Empty](str)
+      else VerifiedString[NonEmpty](str)
+
+    def isEmptyOrWhitespace: Boolean = str.trim.isEmpty
+    def isNullOrEmptyOrWhitespace: Boolean =
+      str == null || str.isEmptyOrWhitespace
+
+  extension (vstr: VerifiedString[NonEmpty]) def value: String = vstr

scala-core-modules/scala-strings-2/src/test/scala/com/baeldung/scala/strings/checkempty/EmptyPatternMatchingUnitTest.scala

@@ -0,0 +1,39 @@
+package com.baeldung.scala.strings.checkempty
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+import EmptyPatternMatchingExtensions._
+
+class EmptyPatternMatchingUnitTest extends AnyFlatSpec with Matchers {
+  "isNullOrEmpty" should "return true for null reference" in {
+    val seq: Seq[?] = null
+    seq.isNullOrEmpty.shouldBe(true)
+  }
+
+  it should "return true for empty sequences" in {
+    val seq: Seq[Any] = Seq.empty
+    seq.isNullOrEmpty.shouldBe(true)
+  }
+
+  "isNullOrEmptyOrWhitespace" should "return true for null strings" in {
+    val str: String = null
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for empty strings" in {
+    val str: String = ""
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for strings with only whitespace" in {
+    val str: String = "   "
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return false for non-empty strings" in {
+    val str: String = "Hello, Scala"
+    str.isNullOrEmptyOrWhitespace.shouldBe(false)
+  }
+
+}

scala-core-modules/scala-strings-2/src/test/scala/com/baeldung/scala/strings/checkempty/EmptySeqUnitTest.scala

@@ -0,0 +1,39 @@
+package com.baeldung.scala.strings.checkempty
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+import EmptySeqExtensions._
+
+class EmptySeqUnitTest extends AnyFlatSpec with Matchers {
+  "isNullOrEmpty" should "return true for null reference" in {
+    val seq: Seq[?] = null
+    seq.isNullOrEmpty.shouldBe(true)
+  }
+
+  it should "return true for empty sequences" in {
+    val seq: Seq[Any] = Seq.empty
+    seq.isNullOrEmpty.shouldBe(true)
+  }
+
+  "isNullOrEmptyOrWhitespace" should "return true for null strings" in {
+    val str: String = null
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for empty strings" in {
+    val str: String = ""
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for strings with only whitespace" in {
+    val str: String = "   "
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return false for non-empty strings" in {
+    val str: String = "Hello, Scala"
+    str.isNullOrEmptyOrWhitespace.shouldBe(false)
+  }
+
+}

scala-core-modules/scala-strings-2/src/test/scala/com/baeldung/scala/strings/checkempty/EmptyStringUnitTest.scala

@@ -0,0 +1,28 @@
+package com.baeldung.scala.strings.checkempty
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+import EmptyStringExtensions._
+
+class EmptyStringUnitTest extends AnyFlatSpec with Matchers {
+
+  "isNullOrEmptyOrWhitespace" should "return true for null strings" in {
+    val str: String = null
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for empty strings" in {
+    val str: String = ""
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for strings with only whitespace" in {
+    val str: String = "   "
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return false for non-empty strings" in {
+    val str: String = "Hello, Scala"
+    str.isNullOrEmptyOrWhitespace.shouldBe(false)
+  }
+}

scala-core-modules/scala-strings-2/src/test/scala/com/baeldung/scala/strings/checkempty/VerifiedStringUnitTest.scala

@@ -0,0 +1,30 @@
+package com.baeldung.scala.strings.checkempty
+
+import com.baeldung.scala.strings.checkempty.VerifiedString.*
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class VerifiedStringUnitTest extends AnyFlatSpec with Matchers {
+
+  def lenght(str: VerifiedString[NonEmpty]) = str.length
+
+  "a verified string" should "never be empty" in {
+    val str: String = null
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for empty strings" in {
+    val str: String = ""
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return true for strings with only whitespace" in {
+    val str: String = "   "
+    str.isNullOrEmptyOrWhitespace.shouldBe(true)
+  }
+
+  it should "return false for non-empty strings" in {
+    val str: String = "Hello, Scala"
+    str.isNullOrEmptyOrWhitespace.shouldBe(false)
+  }
+}