added ex U

src/exercises/ex_u/TestingCountDownLatch_FamilyTrip.java

@@ -0,0 +1,23 @@
+package exercises.ex_u;
+
+import java.util.concurrent.CountDownLatch;
+
+public class TestingCountDownLatch_FamilyTrip {
+    public static void main(String[] args) throws InterruptedException {
+        Vehicle seatAlhambra = new Vehicle();
+        seatAlhambra.printVehicleContent();
+        String[] family = {"Jean", "Anna", "Joseph", "Martha", "Eleonore", "Paul", "Catarina"};
+        // Create a countDownLatch
+        CountDownLatch countDownLatch = new CountDownLatch(family.length);
+
+        // Start the family members
+        // and synchronize them before the start
+        for (int i = 0; i < family.length; i++) {
+            new Thread(new FamilyMember(family[i], seatAlhambra, countDownLatch)).start();
+        }
+        countDownLatch.await();
+
+        seatAlhambra.printVehicleContent();
+        System.out.println("Family trip can start");
+    }
+}