Update AbstractBaseGraph.java

guava/src/com/google/common/graph/AbstractBaseGraph.java

@@ -31,6 +31,9 @@
 import com.google.common.primitives.Ints;
 import java.util.AbstractSet;
 import java.util.Set;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.HashMap;
 import org.jspecify.annotations.Nullable;
 
 /**
@@ -63,6 +66,9 @@ protected long edgeCount() {
    * An implementation of {@link BaseGraph#edges()} defined in terms of {@link Graph#nodes()} and
    * {@link #successors(Object)}.
    */
+ // Cache for edges
+    private transient Set<EndpointPair<N>> cachedEdges;
+
   @Override
   public Set<EndpointPair<N>> edges() {
     return new AbstractSet<EndpointPair<N>>() {
@@ -104,34 +110,45 @@ public ElementOrder<N> incidentEdgeOrder() {
   }
 
   @Override
-  public Set<EndpointPair<N>> incidentEdges(N node) {
-    checkNotNull(node);
-    checkArgument(nodes().contains(node), "Node %s is not an element of this graph.", node);
-    IncidentEdgeSet<N> incident =
-        new IncidentEdgeSet<N>(this, node) {
-          @Override
-          public UnmodifiableIterator<EndpointPair<N>> iterator() {
-            if (graph.isDirected()) {
-              return Iterators.unmodifiableIterator(
-                  Iterators.concat(
-                      Iterators.transform(
-                          graph.predecessors(node).iterator(),
-                          (N predecessor) -> EndpointPair.ordered(predecessor, node)),
-                      Iterators.transform(
-                          // filter out 'node' from successors (already covered by predecessors,
-                          // above)
-                          Sets.difference(graph.successors(node), ImmutableSet.of(node)).iterator(),
-                          (N successor) -> EndpointPair.ordered(node, successor))));
-            } else {
-              return Iterators.unmodifiableIterator(
-                  Iterators.transform(
-                      graph.adjacentNodes(node).iterator(),
-                      (N adjacentNode) -> EndpointPair.unordered(node, adjacentNode)));
-            }
-          }
-        };
-    return nodeInvalidatableSet(incident, node);
-  }
+    public Set<EndpointPair<N>> edges() {
+        if (cachedEdges == null) {
+            cachedEdges = new AbstractSet<EndpointPair<N>>() {
+                @Override
+                public Iterator<EndpointPair<N>> iterator() {
+                    return endpointPairIterator();
+                }
+
+                @Override
+                public int size() {
+                    return edgeCount();
+                }
+
+                @Override
+                public boolean contains(Object obj) {
+                    if (!(obj instanceof EndpointPair)) {
+                        return false;
+                    }
+                    EndpointPair<?> endpointPair = (EndpointPair<?>) obj;
+                    return isDirected() == endpointPair.isOrdered()
+                            && nodes().contains(endpointPair.nodeU())
+                            && successors((N) endpointPair.nodeU()).contains(endpointPair.nodeV());
+                }
+            };
+        }
+        return cachedEdges;
+    }
+
+      // Method to clear the cache when the graph is modified
+    protected void clearCache() {
+        cachedEdges = null;
+    }
+
+  // Abstract methods that subclasses must implement
+    protected abstract Iterator<EndpointPair<N>> endpointPairIterator();
+    protected abstract int edgeCount();
+    protected abstract boolean isDirected();
+    protected abstract Set<N> nodes();
+    protected abstract Set<N> successors(N node);
 
   @Override
   public int degree(N node) {