1 files changed, 44 insertions, 0 deletions
diff --git a/javaparser-core/src/main/java/com/github/javaparser/printer/lexicalpreservation/changes/ListReplacementChange.java b/javaparser-core/src/main/java/com/github/javaparser/printer/lexicalpreservation/changes/ListReplacementChange.java
new file mode 100644
index 000000000..ccb0eada5
--- /dev/null
+++ b/javaparser-core/src/main/java/com/github/javaparser/printer/lexicalpreservation/changes/ListReplacementChange.java
@@ -0,0 +1,44 @@
+package com.github.javaparser.printer.lexicalpreservation.changes;
+
+import com.github.javaparser.ast.Node;
+import com.github.javaparser.ast.NodeList;
+import com.github.javaparser.ast.observer.ObservableProperty;
+import com.github.javaparser.utils.Pair;
+
+import java.util.Optional;
+
+/**
+ * The replacement of an element in a list.
+ */
+public class ListReplacementChange implements Change {
+    private final ObservableProperty observableProperty;
+    private final int index;
+    private final Node newValue;
+
+    public ListReplacementChange(ObservableProperty observableProperty, int index, Node newValue) {
+        this.observableProperty = observableProperty;
+        this.index = index;
+        this.newValue = newValue;
+    }
+
+    @Override
+    public Object getValue(ObservableProperty property, Node node) {
+        if (property == observableProperty) {
+            NodeList nodeList = new NodeList();
+            Object currentRawValue = new NoChange().getValue(property, node);
+            if (currentRawValue instanceof Optional) {
+                Optional optional = (Optional)currentRawValue;
+                currentRawValue = optional.orElseGet(null);
+            }
+            if (!(currentRawValue instanceof NodeList)){
+                throw new IllegalStateException("Expected NodeList, found " + currentRawValue.getClass().getCanonicalName());
+            }
+            NodeList currentNodeList = (NodeList)currentRawValue;
+            nodeList.addAll(currentNodeList);
+            nodeList.set(index, newValue);
+            return nodeList;
+        } else {
+            return new NoChange().getValue(property, node);
+        }
+    }
+}