Add String::capitalize and String::decapitalize`

Author: JavierSegoviaCordoba

CHANGELOG.md

@@ -4,6 +4,9 @@
 
 ### Added
 
+- `String::capitalize`
+- `String::decapitalize`
+
 ### Changed
 
 ### Deprecated

kotlin-stdlib/api/android/kotlin-stdlib.api

@@ -142,6 +142,8 @@ public final class com/javiersc/kotlin/stdlib/AnsiColorsKt {
 }
 
 public final class com/javiersc/kotlin/stdlib/CollectionsKt {
+	public static final fun capitalize (Ljava/lang/String;)Ljava/lang/String;
+	public static final fun decapitalize (Ljava/lang/String;)Ljava/lang/String;
 	public static final fun fifth (Ljava/lang/Iterable;)Ljava/lang/Object;
 	public static final fun fifthOrNull (Ljava/lang/Iterable;)Ljava/lang/Object;
 	public static final fun forth (Ljava/lang/Iterable;)Ljava/lang/Object;

kotlin-stdlib/api/jvm/kotlin-stdlib.api

@@ -142,6 +142,8 @@ public final class com/javiersc/kotlin/stdlib/AnsiColorsKt {
 }
 
 public final class com/javiersc/kotlin/stdlib/CollectionsKt {
+	public static final fun capitalize (Ljava/lang/String;)Ljava/lang/String;
+	public static final fun decapitalize (Ljava/lang/String;)Ljava/lang/String;
 	public static final fun fifth (Ljava/lang/Iterable;)Ljava/lang/Object;
 	public static final fun fifthOrNull (Ljava/lang/Iterable;)Ljava/lang/Object;
 	public static final fun forth (Ljava/lang/Iterable;)Ljava/lang/Object;

kotlin-stdlib/common/main/kotlin/com/javiersc/kotlin/stdlib/Collections.kt

@@ -2,6 +2,24 @@
 
 package com.javiersc.kotlin.stdlib
 
+/**
+ * Returns a copy of this string having its first letter title-cased using the rules of the default
+ * locale, or the original string if it's empty or already starts with a title case letter.
+ *
+ * The title case of a character is usually the same as its upper case with several exceptions. The
+ * particular list of characters with the special title case form depends on the underlying
+ * platform.
+ */
+public inline fun String.capitalize(): String = replaceFirstChar {
+    if (it.isLowerCase()) it.titlecase() else it.toString()
+}
+
+/**
+ * Returns a copy of this string having its first letter lowercased using the rules of the default
+ * locale, or the original string if it's empty or already starts with a lower case letter.
+ */
+public inline fun String.decapitalize(): String = replaceFirstChar { it.lowercase() }
+
 /**
  * Returns second element.
  *

kotlin-stdlib/common/test/kotlin/com/javiersc/kotlin/stdlib/StringsTest.kt

@@ -6,6 +6,20 @@ import kotlin.test.assertTrue
 
 class StringsTest {
 
+    @Test
+    fun string_capitalize() {
+        assertTrue { "hello".capitalize() == "Hello" }
+        assertTrue { "Hello".capitalize() == "Hello" }
+        assertTrue { "hElLo".capitalize() == "HElLo" }
+    }
+
+    @Test
+    fun string_decapitalize() {
+        assertTrue { "hello".decapitalize() == "hello" }
+        assertTrue { "Hello".decapitalize() == "hello" }
+        assertTrue { "HElLo".decapitalize() == "hElLo" }
+    }
+
     @Test
     fun string_remove() {
         assertTrue { "Hello, World".remove("Hello, ") == "World" }
@@ -41,15 +55,15 @@ class StringsTest {
     }
 
     @Test
-    fun remove_duplicate_empty_lines() {
+    fun string_remove_duplicate_empty_lines() {
         assertTrue { "a\nb\n\n\nc\n".removeDuplicateEmptyLines() == "a\nb\n\nc\n" }
         assertTrue { "a\n\nb\n\n\nc\n".removeDuplicateEmptyLines() == "a\n\nb\n\nc\n" }
         assertTrue { "a\n\nb\n\n\nc\n\n".removeDuplicateEmptyLines() == "a\n\nb\n\nc\n" }
         assertTrue { "a\n\n\n\n\nb\n\n".removeDuplicateEmptyLines() == "a\n\nb\n" }
     }
 
     @Test
-    fun end_with_new_line() {
+    fun string_end_with_new_line() {
         assertTrue { "a".endWithNewLine() == "a\n" }
         assertTrue { "a\n".endWithNewLine() == "a\n" }
         assertTrue { "".endWithNewLine() == "" }