fix: union

logic-ng · Jan 21, 2020 · 5d93520 · 5d93520
1 parent 72ebef6
commit 5d93520
Show file tree

Hide file tree

Showing 2 changed files with 9 additions and 3 deletions.
diff --git a/src/main/java/org/logicng/util/CollectionHelper.java b/src/main/java/org/logicng/util/CollectionHelper.java
@@ -58,9 +58,15 @@ public static <T, C extends Collection<T>> C intersection(final Collection<T> co
      * @return the union of the two collections as a set
      */
     public static <T, C extends Collection<T>> C union(final Collection<T> col1, final Collection<T> col2, final Supplier<C> collectionFactory) {
-        if (col1 == null || col2 == null) {
+        if (col1 == null && col2 == null) {
             return collectionFactory.get();
         }
+        if (col1 == null) {
+            return col2.stream().distinct().collect(Collectors.toCollection(collectionFactory));
+        }
+        if (col2 == null) {
+            return col1.stream().distinct().collect(Collectors.toCollection(collectionFactory));
+        }
         return Stream.concat(col1.stream(), col2.stream()).distinct().collect(Collectors.toCollection(collectionFactory));
     }
 

diff --git a/src/test/java/org/logicng/util/CollectionHelperTest.java b/src/test/java/org/logicng/util/CollectionHelperTest.java
@@ -41,8 +41,8 @@ public void testIntersection() {
     public void testUnion() {
         final List<String> strings1 = Arrays.asList("a", "b", "c", "a");
         List<String> strings2 = Arrays.asList("c", "d", "e");
-        assertThat(CollectionHelper.<String, TreeSet<String>>union(strings1, null, TreeSet::new)).isEmpty();
-        assertThat(CollectionHelper.<String, TreeSet<String>>union(null, strings2, TreeSet::new)).isEmpty();
+        assertThat(CollectionHelper.<String, TreeSet<String>>union(strings1, null, TreeSet::new)).containsExactly("a", "b", "c");
+        assertThat(CollectionHelper.<String, TreeSet<String>>union(null, strings2, TreeSet::new)).containsExactly("c", "d", "e");
         assertThat(CollectionHelper.<String, TreeSet<String>>union(strings1, strings2, TreeSet::new)).containsExactly("a", "b", "c", "d", "e");
         strings2 = Arrays.asList("c", "d", "e", "a", "a", "a");
         assertThat(CollectionHelper.<String, List<String>>union(strings1, strings2, ArrayList::new)).containsExactly("a", "b", "c", "d", "e");