updated Random() to SecureRandom() (#1670)

* updated Random() to SecureRandom()

* batch 2 of SecureRandom updates

leader-followers/src/main/java/com/iluwatar/leaderfollowers/App.java

@@ -23,7 +23,7 @@
 
 package com.iluwatar.leaderfollowers;
 
-import java.util.Random;
+import java.security.SecureRandom;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 
@@ -84,7 +84,7 @@ public class App {
    * Add tasks.
    */
   private static void addTasks(TaskSet taskSet) throws InterruptedException {
-    var rand = new Random();
+    var rand = new SecureRandom();
     for (var i = 0; i < 5; i++) {
       var time = Math.abs(rand.nextInt(1000));
       taskSet.addTask(new Task(time));