[KTLN-713] Remove Null and Empty Values from a List in Kotlin (#757)

* fixed Unit test

* code cleanup

Author: albertache1998

core-kotlin-modules/core-kotlin-collections-list-2/src/test/kotlin/removeNullAndEmptyValues/RemoveNullAndEmptyValuesUnitTest.kt

@@ -0,0 +1,44 @@
+package removeNullAndEmptyValues
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class RemoveNullAndEmptyValuesUnitTest {
+
+    @Test
+    fun `remove null and empty values from list via list iteration`() {
+        val listWithNullsAndEmpty: MutableList<String?> = mutableListOf("A", null, "", "C", null, "E")
+        val listWithoutNullsAndEmpty = removeValuesViaIteration(listWithNullsAndEmpty)
+        assertEquals(listOf("A", "C", "E"), listWithoutNullsAndEmpty)
+    }
+
+    @Test
+    fun `remove null and empty values from list using filterNotNull and filterNot methods`() {
+        val listWithNullsAndEmpty: List<String?> = listOf("A", null, "", "C", null, "E")
+        val listWithoutNulls: List<String> = listWithNullsAndEmpty.filterNotNull()
+
+        val listWithoutNullsAndEmpty: List<String> = listWithoutNulls.filterNot { it.isEmpty() }
+
+        assertEquals(listOf("A", "", "C", "E"), listWithoutNulls)
+        assertEquals(listOf("A", "C", "E"), listWithoutNullsAndEmpty)
+    }
+
+    @Test
+    fun `remove null and empty values from list using removeIf method`() {
+        val listWithNullsAndEmpty: MutableList<String?> = mutableListOf("A", null, "", "C", null, "E")
+        listWithNullsAndEmpty.removeIf { it == null || it.isEmpty() }
+
+        assertEquals(listOf("A", "C", "E"), listWithNullsAndEmpty)
+    }
+
+    fun removeValuesViaIteration(listWithNullsAndEmpty: MutableList<String?>): List<String> {
+        val iterator = listWithNullsAndEmpty.iterator()
+        while (iterator.hasNext()) {
+            val element = iterator.next()
+            if (element == null || element.isEmpty()) {
+                iterator.remove()
+            }
+        }
+        return listWithNullsAndEmpty as List<String>
+    }
+}