Added a test to confirm that builders correctly support null elements in collections

Author: YetAnotherMatt

kotlin-builder-example-usage/src/main/kotlin/com/thinkinglogic/example/CollectionsDataClass.kt

@@ -8,6 +8,7 @@ import java.util.*
 @Builder
 data class CollectionsDataClass(
         val listOfStrings: List<String>,
+        @NullableType val listOfNullableStrings: List<String?>,
         val setOfLongs: Set<Long>,
         @NullableType val setOfNullableLongs: Set<Long?>,
         val hashSet: HashSet<Long>,

kotlin-builder-example-usage/src/test/java/com/thinkinglogic/example/CollectionsDataClassJavaTest.java

@@ -0,0 +1,46 @@
+package com.thinkinglogic.example;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+import java.util.*;
+
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.emptySet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
+import static org.assertj.core.api.BDDAssertions.then;
+
+public class CollectionsDataClassJavaTest {
+
+    @Test
+    void builderShouldAllowNullValuesInCollections() {
+        // given
+        CollectionsDataClassBuilder builder = new CollectionsDataClassBuilder();
+
+        List<String> nullableList = asList(null, null, "foo");
+        Set<Long> nullableSet = new HashSet<>(asList(null, null, 1L));
+
+        HashMap<String, LocalDate> nullableMap = new HashMap<>();
+        nullableMap.put("Foo", null);
+
+
+        // when
+        CollectionsDataClass result = builder
+                .listOfNullableStrings(nullableList)
+                .mapOfStringToNullableDates(nullableMap)
+                .setOfNullableLongs(nullableSet)
+                .collectionOfDates(emptySet())
+                .listOfStrings(emptyList())
+                .setOfLongs(emptySet())
+                .hashSet(new HashSet<>())
+                .treeMap(new TreeMap<>())
+                .build();
+
+        // then
+        assertThat(result.getListOfNullableStrings()).isEqualTo(nullableList);
+        assertThat(result.getMapOfStringToNullableDates()).isEqualTo(nullableMap);
+        assertThat(result.getSetOfNullableLongs()).isEqualTo(nullableSet);
+    }
+}

kotlin-builder-example-usage/src/test/kotlin/com/thinkinglogic/example/CollectionsDataClassTest.kt

@@ -14,6 +14,7 @@ internal class CollectionsDataClassTest {
                 hashSet = HashSet(setOf(1L, 2L)),
                 collectionOfDates = listOf(LocalDate.now()),
                 listOfStrings = listOf("Foo", "bar"),
+                listOfNullableStrings = listOf("Foo", "bar", null, null),
                 setOfLongs = setOf(3L, 4L),
                 setOfNullableLongs = setOf(3L, null),
                 treeMap = TreeMap(),
@@ -25,6 +26,7 @@ internal class CollectionsDataClassTest {
                 .hashSet(expected.hashSet)
                 .collectionOfDates(expected.collectionOfDates)
                 .listOfStrings(expected.listOfStrings)
+                .listOfNullableStrings(expected.listOfNullableStrings)
                 .setOfLongs(expected.setOfLongs)
                 .setOfNullableLongs(expected.setOfNullableLongs)
                 .treeMap(expected.treeMap)