Fix error in prepareFolds method

src/main/java/be/cylab/java/wowa/training/Example.java

@@ -63,10 +63,10 @@ public final class Example {
         Trainer trainer = new Trainer(parameters, new SolutionDistance(5));
 
         long start_time = System.currentTimeMillis();
-        AbstractSolution solution = trainer.run(
-                "./ressources/webshell_data.json",
-                "./ressources/webshell_expected.json");
-        System.out.println(solution);
+        //AbstractSolution solution = trainer.run(
+        //        "./ressources/webshell_data.json",
+        //        "./ressources/webshell_expected.json");
+        //System.out.println(solution);
         long end_time = System.currentTimeMillis();
         logger.log(Level.INFO, "Execution time : "
                 + (end_time - start_time) / 1000 + " seconds");

src/main/java/be/cylab/java/wowa/training/Trainer.java

@@ -188,8 +188,9 @@ public class Trainer {
             TrainingDataset tmp = new TrainingDataset();
             int alert_counter = 0;
             int no_alert_counter = 0;
-            while (tmp.getLength() < (alert_counter + no_alert_counter)) {
-                int index = Utils.randomInteger(0, dataset.getLength());
+            System.out.println("Fold " + i);
+            while (tmp.getLength() < (alert_number + no_alert_number)) {
+                int index = Utils.randomInteger(0, dataset.getLength() - 1);
                 if (dataset.getExpected().get(index) == 1
                         && alert_counter < alert_number) {
                     tmp.addElementInDataset(dataset, index);

src/main/java/be/cylab/java/wowa/training/TrainingDataset.java

@@ -108,11 +108,12 @@ class TrainingDataset {
      * @param data_to_add
      * @param index
      */
-    void addFoldInDataset(
+    TrainingDataset addFoldInDataset(
             final List<TrainingDataset> data_to_add,
             final int index) {
         this.data.addAll(data_to_add.get(index).data);
         this.expected.addAll(data_to_add.get(index).expected);
         this.length++;
+        return this;
     }
 }