DiffCursor value comparison support for null values.

in case null != default

1 files changed, 9 insertions, 7 deletions

diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapDiffCursor.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapDiffCursor.java
index beaff13b..6c076ce5 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapDiffCursor.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapDiffCursor.java
@@ -5,6 +5,7 @@ import tools.refinery.store.map.ContinousHashProvider;
 import tools.refinery.store.map.Cursor;
 import tools.refinery.store.map.DiffCursor;
 
+import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -121,7 +122,7 @@ public class MapDiffCursor<K, V> implements DiffCursor<K, V>, Cursor<K, V> {
                         this.fromValue = defaultValue;
                         this.toValue = cursor2.value;
                 } else {
-                        throw new IllegalArgumentException("Inconsistent compare result for diffcursor");
+                        throw new IllegalArgumentException("Inconsistent compare result for diffCursor");
                 }
         }
 
@@ -145,16 +146,17 @@ public class MapDiffCursor<K, V> implements DiffCursor<K, V>, Cursor<K, V> {
                         this.fromValue = defaultValue;
                         this.toValue = cursor2.value;
                 }
-                default -> throw new IllegalArgumentException("Inconsistent compare result for diffcursor");
+                default -> throw new IllegalArgumentException("Inconsistent compare result for diffCursor");
                 }
         }
 
+        /**
+         * Checks if two states has the same values, i.e., there is no difference.
+         * @return whether two states has the same values
+         */
         protected boolean sameValues() {
-                if (this.fromValue == null) {
-                        return this.toValue == null;
-                } else {
-                        return this.fromValue.equals(this.toValue);
-                }
+                if(cursor1.isTerminated() || cursor2.isTerminated()) return false;
+                else return Objects.equals(this.fromValue, this.toValue);
         }
 
         protected boolean moveOne() {