Missed the ugly solution from map.put

1 files changed, 19 insertions, 0 deletions

diff --git a/model-data/src/main/java/org/eclipse/viatra/solver/data/map/internal/OldValueBox.java b/model-data/src/main/java/org/eclipse/viatra/solver/data/map/internal/OldValueBox.java
new file mode 100644
index 00000000..23502857
--- /dev/null
+++ b/model-data/src/main/java/org/eclipse/viatra/solver/data/map/internal/OldValueBox.java
@@ -0,0 +1,19 @@
+package org.eclipse.viatra.solver.data.map.internal;
+
+public class OldValueBox<V>{
+        V oldValue;
+        boolean isSet = false;
+
+        public V getOldValue() {
+                if(!isSet) throw new IllegalStateException();
+                isSet = false;
+                return oldValue;
+        }
+
+        public void setOldValue(V ouldValue) {
+                if(isSet) throw new IllegalStateException();
+                this.oldValue = ouldValue;
+                isSet = true;
+        }
+        
+}