Solutions/generics/03 (#73)

* Update SchoolClass.java

In the loop condition, pupils.size() is re-evaluated in each iteration, and because the code removed pupils from the list inside the loop, the size of the list decreases with each iteration. This is not clean and because of this an exception occurred when trying to run the function with an even amount of pupils. 

Furthermore the if condition to check if the size of the array is 1 needed also to be inside the loop for this solution.

* Update Exercise.java

Add example for even pupils

* Use while loop

---------

Co-authored-by: SteffenLm <33038091+SteffenLm@users.noreply.github.com>

Author: jeremistderechte

Exercise.java

@@ -13,6 +13,7 @@ public static void main(String[] args) {
     schoolClass.addPupil(new Pupil("Max", "m"));
     schoolClass.addPupil(new Pupil("Franziska", "w"));
     schoolClass.addPupil(new Pupil("Jennifer", "w"));
+    //schoolClass.addPupil(new Pupil("Jeremy", "m"));
 
     schoolClass.getPairs().forEach(System.out::println);
   }

SchoolClass.java

@@ -10,19 +10,18 @@ public void addPupil(Pupil pupil) {
 
   public List<Pair<Pupil>> getPairs() {
     List<Pair<Pupil>> pairs = new ArrayList<>();
-
-    for (int i = 0; i < pupils.size(); i++) {
-      Pupil single1 = pupils.get((new Random().nextInt(pupils.size())));
-      pupils.remove(single1);
-      Pupil single2 = pupils.get((new Random().nextInt(pupils.size())));
-      pupils.remove(single2);
-      pairs.add(new Pair<Pupil>(single1, single2));
-    }
-
-    if (pupils.size() == 1) {
-      pairs.add(new Pair<Pupil>(pupils.get(0), null));
+    while (pupils().size() > 0) {
+      if (pupils.size() == 1) {
+        pairs.add(new Pair<Pupil>(pupils().get(0), null));
+        pupils().clear();
+      } else {
+        Pupil single1 = pupils.get((new Random().nextInt(pupils.size())));
+        pupils.remove(single1);
+        Pupil single2 = pupils.get((new Random().nextInt(pupils.size())));
+        pupils.remove(single2);
+        pairs.add(new Pair<Pupil>(single1, single2));
+      }
     }
-
     return pairs;
   }
 }