General performance improvement (#6078)

src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java

@@ -42,9 +42,7 @@ public class FloydWarshall {
     public void floydwarshall(int[][] adjacencyMatrix) {
         // Initialize the distance matrix with the adjacency matrix.
         for (int source = 1; source <= numberofvertices; source++) {
-            for (int destination = 1; destination <= numberofvertices; destination++) {
-                distanceMatrix[source][destination] = adjacencyMatrix[source][destination];
-            }
+            System.arraycopy(adjacencyMatrix[source], 1, distanceMatrix[source], 1, numberofvertices);
         }
         for (int intermediate = 1; intermediate <= numberofvertices; intermediate++) {
             for (int source = 1; source <= numberofvertices; source++) {

src/main/java/com/thealgorithms/datastructures/lists/SinglyLinkedList.java

@@ -403,7 +403,7 @@ public class SinglyLinkedList implements Iterable<Integer> {
         SinglyLinkedList list = new SinglyLinkedList();
         assert list.isEmpty();
         assert list.size() == 0 && list.count() == 0;
-        assert list.toString().equals("");
+        assert list.toString().isEmpty();
 
         /* Test insert function */
         list.insertHead(5);

src/main/java/com/thealgorithms/datastructures/trees/GenericTree.java

@@ -23,6 +23,7 @@ public class GenericTree {
     }
 
     private final Node root;
+
     public GenericTree() { // Constructor
         Scanner scn = new Scanner(System.in);
         root = createTreeG(null, 0, scn);
@@ -225,8 +226,6 @@ public class GenericTree {
         for (int i = 0; i < node.child.size(); i++) {
             if (node.child.get(i).child.size() == 0) {
                 arr.add(i);
-                // node.child.remove(i);
-                // i--;
             } else {
                 removeleaves(node.child.get(i));
             }