Replaced all usages of deprecated toUpperCase/toLowerCase with uppercase/lowercase calls

Functional Programming/Lambdas/Examples/src/OmittingParentheses.kt

@@ -4,6 +4,6 @@ import atomictest.eq
 fun main() {
   val list = listOf('a', 'b', 'c', 'd')
   val result =
-    list.map { "[${it.toUpperCase()}]" }
+    list.map { "[${it.uppercaseChar()}]" }
   result eq listOf("[A]", "[B]", "[C]", "[D]")
 }

Introduction to Objects/Creating Classes/Exercise 4/src/Task.kt

@@ -2,9 +2,9 @@
 package creatingClassesExercise4
 
 fun main() {
-  val s: String = "Hello!"
-  println(s.toUpperCase())
-  println(s.toLowerCase())
+  val s = "Hello!"
+  println(s.uppercase())
+  println(s.lowercase())
 }
 /* Output:
 HELLO!

Introduction to Objects/Creating Classes/Exercise 4/task.md

@@ -7,7 +7,7 @@ Press <span class="shortcut">&shortcut:QuickJavaDoc;</span> when the caret is
 on a class or a function usage, and IntelliJ IDEA will show you the available
 documentation for this function or class.
 
-Put the caret on the `String` type and its `toUpperCase()` and `toLowerCase()` member
+Put the caret on the `String` type and its `uppercase()` and `lowercase()` member
 functions, then use <span class="control">`Quick Documentation`</span>.
 Press <span class="shortcut">&shortcut:EditorEscape;</span> to close the
 quick documentation pop-up.

Introduction to Objects/Objects Everywhere/Examples/src/Strings.kt

@@ -3,7 +3,7 @@
 fun main() {
   val s = "AbcD"
   println(s.reversed())
-  println(s.toLowerCase())
+  println(s.lowercase())
 }
 /* Output:
 DcbA

Introduction to Objects/Objects Everywhere/Exercise 2/src/Task.kt

@@ -5,7 +5,7 @@ fun isPalindrome(s: String): Boolean =
   s.reversed() == s
 
 fun isPalIgnoreCase(s: String): Boolean =
-  isPalindrome(s.toLowerCase())
+  isPalindrome(s.lowercase())
 
 fun main() {
   println(isPalIgnoreCase("Mom"))  // true

Introduction to Objects/Objects Everywhere/Exercise 2/task-info.yaml

@@ -4,7 +4,7 @@ files:
   visible: true
   placeholders:
   - offset: 170
-    length: 29
+    length: 27
     placeholder_text: TODO()
 - name: test/Tests.kt
   visible: false

Introduction to Objects/Objects Everywhere/Exercise 2/task.md

@@ -5,7 +5,7 @@ palindromes. "Bob" should now be considered a palindrome.
 
 <div class="hint">
 
-Use `toLowerCase()` to produce a `String` with all lower-case characters.
-You can also use `toUpperCase()`.
+Use `lowercase()` to produce a `String` with all lower-case characters.
+You can also use `uppercase()`.
 
 </div>

Introduction to Objects/Objects Everywhere/Exercise 3/src/Task.kt

@@ -5,7 +5,7 @@ fun isPalindrome(s: String): Boolean =
   s.reversed() == s
 
 fun isPalIgnoreCase(s: String): Boolean =
-  isPalindrome(s.toLowerCase())
+  isPalindrome(s.lowercase())
 
 fun isPalIgnoreSpecial(s: String): Boolean {
   var onlyLetters = ""

Introduction to Objects/Objects Everywhere/Exercise 3/task-info.yaml

@@ -3,7 +3,7 @@ files:
 - name: src/Task.kt
   visible: true
   placeholders:
-  - offset: 248
+  - offset: 246
     length: 154
     placeholder_text: TODO()
 - name: test/Tests.kt

Power Tools/Operator Overloading/Examples/src/StringInvoke.kt

@@ -7,6 +7,6 @@ operator fun String.invoke(
 ) = f(this)
 
 fun main() {
-  "mumbling" { it.toUpperCase() } eq
+  "mumbling" { it.uppercase() } eq
     "MUMBLING"
 }

Programming Basics/Data Types/Exercise 1/test/Tests.kt

@@ -20,7 +20,7 @@ class TestDataTypesExercise1 {
   fun checkTypeMismatch() {
     val output = runAndGetSystemOutput {
       main()
-    }.toLowerCase()
+    }.lowercase()
 
     Assert.assertTrue("The first line of the error the compiler produces is expected: Type mismatch",
       output.contains("type")

Usability/Non-Null Assertions/Examples/src/ValueFromMap.kt

@@ -3,13 +3,13 @@ import atomictest.*
 
 fun main() {
   val map = mapOf(1 to "one")
-  map[1]!!.toUpperCase() eq "ONE"
-  map.getValue(1).toUpperCase() eq "ONE"
+  map[1]!!.uppercase() eq "ONE"
+  map.getValue(1).uppercase() eq "ONE"
   capture {
-    map[2]!!.toUpperCase()
+    map[2]!!.uppercase()
   } eq "NullPointerException"
   capture {
-    map.getValue(2).toUpperCase()
+    map.getValue(2).uppercase()
   } eq "NoSuchElementException: " +
     "Key 2 is missing in the map."
 }

Usability/Safe Calls & the Elvis Operator/Examples/src/SafeOperation.kt

@@ -3,9 +3,9 @@ package safecalls
 import atomictest.*
 
 fun String.echo() {
-  trace(toUpperCase())
+  trace(uppercase())
   trace(this)
-  trace(toLowerCase())
+  trace(lowercase())
 }
 
 fun main() {

Usability/Safe Calls & the Elvis Operator/Exercise 1/src/Task.kt

@@ -3,7 +3,7 @@ package safeCallsAndTheElvisOperatorExercise1
 import atomictest.eq
 
 fun downcase(s: String?): String =
-  s?.toLowerCase() ?: ""
+  s?.lowercase() ?: ""
 
 fun main() {
   downcase(null) eq ""

Usability/Safe Calls & the Elvis Operator/Exercise 1/task-info.yaml

@@ -4,9 +4,9 @@ files:
   visible: true
   placeholders:
   - offset: 98
-    length: 59
+    length: 57
     placeholder_text: fun downcase() {}
-  - offset: 172
+  - offset: 170
     length: 49
     placeholder_text: |-
       /*

Usability/Safe Calls & the Elvis Operator/Exercise 1/test/Tests.kt

@@ -9,7 +9,7 @@ class TestSafeCallsAndTheElvisOperatorExercise1 {
         val downcaseFunc = ::downcase
         checkParametersOfTopLevelFunction(downcaseFunc, listOf("" to "kotlin.String?"))
         val actual = downcaseFunc.call(s)
-        Assert.assertEquals("Wrong result for calling downcase(\"$s\")", s?.toLowerCase() ?: "", actual)
+        Assert.assertEquals("Wrong result for calling downcase(\"$s\")", s?.lowercase() ?: "", actual)
     }
 
     @Test