[KTLN-827] Java Boolean.valueOf() Equivalent in Kotlin (#825)

* add unit test

* code fixes

* code fixes

* code fixes

* Removing whitespace check from regex.

Author: albertache1998

core-kotlin-modules/core-kotlin-strings-4/src/test/kotlin/com/baeldung/booleanValueOfKotlinEquivalent/BooleanValueOfKotlinEquivalentUnitTest.kt

@@ -0,0 +1,81 @@
+package com.baeldung.booleanValueOfKotlinEquivalent
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertThrows
+import org.junit.jupiter.api.Test
+
+class BooleanValueOfKotlinEquivalentUnitTest {
+
+    @Test
+    fun `obtain equivalent in Kotlin by string comparison using equals method`() {
+        assertEquals(true, convertStringToBoolean("true"))
+        assertEquals(true, convertStringToBoolean("TRUE"))
+        assertEquals(false, convertStringToBoolean("false"))
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using toBoolean method`() {
+        assertEquals(true, "true".toBoolean())
+        assertEquals(true, "TRUE".toBoolean())
+        assertEquals(false, "false".toBoolean())
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using toBooleanStrictOrNull method`() {
+        var str: String? = "fjdfj"
+        assertEquals(true, "true".toBooleanStrictOrNull())
+        assertEquals(null, str?.toBooleanStrictOrNull())
+        assertEquals(false, "false".toBooleanStrictOrNull())
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using toBooleanStrict method`() {
+        assertEquals(true, "true".toBooleanStrict())
+        assertEquals(false, "false".toBooleanStrict())
+        assertThrows(IllegalArgumentException::class.java) {
+            "TRUE".toBooleanStrict()
+        }
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using parseBoolean method`() {
+        assertEquals(true, java.lang.Boolean.parseBoolean("true"))
+        assertEquals(true, java.lang.Boolean.parseBoolean("TRUE"))
+        assertEquals(false, java.lang.Boolean.parseBoolean("false"))
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using valueOf method`() {
+        assertEquals(true, java.lang.Boolean.valueOf("true"))
+        assertEquals(true, java.lang.Boolean.valueOf("TRUE"))
+        assertEquals(false, java.lang.Boolean.valueOf("false"))
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using custom extension function`() {
+        assertEquals(true, "true".toBooleanValue())
+        assertEquals(true, "TRUE".toBooleanValue())
+        assertEquals(false, "false".toBooleanValue())
+    }
+
+    @Test
+    fun `obtain equivalent in Kotlin using regex`() {
+        assertEquals(true, convertStringToBooleanUsingRegex("true"))
+        assertEquals(true, convertStringToBooleanUsingRegex("TRUE"))
+        assertEquals(false, convertStringToBooleanUsingRegex("false"))
+    }
+
+}
+fun convertStringToBoolean(input: String): Boolean {
+    return if (input.equals("true", ignoreCase = true)) true else false
+}
+
+fun convertStringToBooleanUsingRegex(input: String): Boolean {
+    return input.trim().matches("^(?i:true)$".toRegex())
+}
+
+fun String.toBooleanValue(): Boolean =
+    when (this.toLowerCase()) {
+        "true" -> true
+        else -> false
+    }