Step 8: Seven code quality improvements

1. Remove 32 trivial checkParameters() { return null; } overrides — default already on Parametrizable
2. Clean up dead variables and commented-out experimental code in Estrada/LaplacianEstrada
3. Extract concatWithArrayCopy() to AlgorithmUtils.concatArrays(); remove 6 duplicate copies
4. Add AlgorithmUtils.getEccentricities(); eliminate duplicated max-distance loop in AllEccen,
   TotalEccentricityIndex, EccentricityComplexityIndex; AllEccen now delegates to Eccentricity.eccentricity()
5. Introduce WienerIndexBase to consolidate FloydWarshall boilerplate and getCategory() across
   WienerIndex, MWienerIndex, EccentricWienerIndex
6. Remove dead private edge_adj() methods from ZagrebCoindex, ZagrebCoindexSelectedEdges,
   ZagrebIndexSelectedEdges (never called in those classes)
7. Override clear() in NotifiableAttributeSetImpl to fire attributeUpdated(name, old, null)
   for each entry, consistent with the notification contract on put()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rostam

src/graphtea/extensions/AlgorithmUtils.java

@@ -908,4 +908,30 @@ public static Matrix getAverageTransMatrix (GraphModel g) {
         }
         return adj;
     }
+
+    /** Concatenates two arrays into a new array of the same component type. */
+    public static <T> T[] concatArrays(T[] array1, T[] array2) {
+        T[] result = Arrays.copyOf(array1, array1.length + array2.length);
+        System.arraycopy(array2, 0, result, array1.length, array2.length);
+        return result;
+    }
+
+    /**
+     * Returns the eccentricity of every vertex: ecc[v] = max distance from v to any reachable vertex.
+     * Unreachable pairs (distance >= n+1 by FloydWarshall convention) are excluded; isolated vertices get 0.
+     */
+    public static int[] getEccentricities(GraphModel g) {
+        FloydWarshall fw = new FloydWarshall();
+        int[][] dist = fw.getAllPairsShortestPathWithoutWeight(g);
+        int n = g.numOfVertices();
+        int[] ecc = new int[n];
+        for (int v = 0; v < n; v++) {
+            for (int u = 0; u < n; u++) {
+                if (u != v && dist[v][u] < n + 1 && dist[v][u] > ecc[v]) {
+                    ecc[v] = dist[v][u];
+                }
+            }
+        }
+        return ecc;
+    }
 }

src/graphtea/extensions/actions/BarycentricSubdivisionGraph.java

@@ -75,10 +75,6 @@ public String getDescription() {
         return "Barycentric Subdivision Graph";
     }
 
-    @Override
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {

src/graphtea/extensions/actions/CircularVisualization.java

@@ -45,9 +45,6 @@ public static void circularVisualize(int r, int x, int y, SubGraph g) {
         }
     }
 
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getName() {

src/graphtea/extensions/actions/Composition.java

@@ -37,10 +37,6 @@ public void action(GraphData graphData) {
         graphData.core.showGraph(g);
     }
 
-    @Override
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {

src/graphtea/extensions/actions/Disjunction.java

@@ -36,10 +36,6 @@ public void action(GraphData graphData) {
         graphData.core.showGraph(g);
     }
 
-    @Override
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {

src/graphtea/extensions/actions/LocalityLens.java

@@ -67,10 +67,6 @@ public String getCategory() {
         return "Visualization";
     }
 
-    @Override
-    public String checkParameters() {
-        return null;
-    }
 }
 
 class MouseEventListener implements Listener {

src/graphtea/extensions/actions/ParalineGraph.java

@@ -34,10 +34,6 @@ public String getDescription() {
         return "Paraline Graph";
     }
 
-    @Override
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {

src/graphtea/extensions/actions/Sum.java

@@ -38,10 +38,6 @@ public void action(GraphData graphData) {
         graphData.core.showGraph(g);
     }
 
-    @Override
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {

src/graphtea/extensions/actions/g6/G6CSVStringLoader.java

@@ -75,9 +75,6 @@ public void action(GraphData graphData) {
         }
     }
 
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {

src/graphtea/extensions/actions/g6/G6Checker.java

@@ -42,9 +42,6 @@ public void action(GraphData graphData) {
         }
     }
 
-    public String checkParameters() {
-        return null;
-    }
 
     @Override
     public String getCategory() {