refactor: consolidate adjacency/neighbor cache to GraphUtils (3 analyzers)

Gvisual/src/gvisual/GrowthRateAnalyzer.java

@@ -118,18 +118,20 @@ private static double computeDensity(int nodes, int edges) {
     private static double computeAvgClustering(Graph<String, edge> g) {
         if (g.getVertexCount() == 0) return 0.0;
 
+        Map<String, Set<String>> adj = GraphUtils.buildAdjacencyMap(g);
         double totalClustering = 0.0;
         for (String v : g.getVertices()) {
-            Collection<String> neighbors = g.getNeighbors(v);
+            Set<String> neighbors = adj.get(v);
             if (neighbors == null) continue;
             List<String> neighborList = new ArrayList<>(neighbors);
             int k = neighborList.size();
             if (k < 2) continue;
 
             int triangles = 0;
             for (int i = 0; i < k; i++) {
+                Set<String> ni = adj.get(neighborList.get(i));
                 for (int j = i + 1; j < k; j++) {
-                    if (g.isNeighbor(neighborList.get(i), neighborList.get(j))) {
+                    if (ni != null && ni.contains(neighborList.get(j))) {
                         triangles++;
                     }
                 }

Gvisual/src/gvisual/NodeSimilarityAnalyzer.java

@@ -81,7 +81,7 @@ public NodeSimilarityAnalyzer(Graph<String, edge> graph) {
             throw new IllegalArgumentException("Graph must not be null");
         }
         this.graph = graph;
-        this.neighborCache = new HashMap<String, Set<String>>();
+        this.neighborCache = GraphUtils.buildAdjacencyMap(graph);
     }
 
     // ── Single-pair metrics ─────────────────────────────────────

Gvisual/src/gvisual/StructuralHoleAnalyzer.java

@@ -51,7 +51,7 @@
 public class StructuralHoleAnalyzer {
 
     private final Graph<String, edge> graph;
-    private Map<String, Set<String>> neighborCache;
+    private final Map<String, Set<String>> neighborCache;
 
     /**
      * Creates a new StructuralHoleAnalyzer for the given graph.
@@ -64,18 +64,7 @@ public StructuralHoleAnalyzer(Graph<String, edge> graph) {
             throw new IllegalArgumentException("Graph must not be null");
         }
         this.graph = graph;
-        buildNeighborCache();
-    }
-
-    private void buildNeighborCache() {
-        neighborCache = new HashMap<>();
-        for (String v : graph.getVertices()) {
-            Set<String> nbrs = new LinkedHashSet<>();
-            for (String n : graph.getNeighbors(v)) {
-                nbrs.add(n);
-            }
-            neighborCache.put(v, nbrs);
-        }
+        this.neighborCache = GraphUtils.buildAdjacencyMap(graph);
     }
 
     // ── Result classes ──────────────────────────────────────────