added ex U

src/exercises/ex_u/FamilyMember.java

@@ -0,0 +1,22 @@
+package exercises.ex_u;
+
+import java.util.concurrent.CountDownLatch;
+
+public class FamilyMember implements Runnable {
+    private final String name;
+    private final Vehicle vehicle;
+    private final CountDownLatch countDownLatch;
+
+    public FamilyMember(String name, Vehicle vehicle, CountDownLatch countDownLatch) {
+        this.name = name;
+        this.vehicle = vehicle;
+        this.countDownLatch = countDownLatch;
+    }
+
+    @Override
+    public void run() {
+        vehicle.addSuitcase(name + "'s suitcase");
+        System.out.println(name + " has loaded their suitcase");
+        countDownLatch.countDown();
+    }
+}

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");
+    }
+}

src/exercises/ex_u/Vehicle.java

@@ -0,0 +1,14 @@
+package exercises.ex_u;
+
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+public class Vehicle {
+    private Queue<String> suitcases = new ConcurrentLinkedQueue<>();
+    public void addSuitcase(String suitcase) {
+        suitcases.add(suitcase);
+    }
+    public void printVehicleContent() {
+        System.out.println("Suitcases: " + suitcases);
+    }
+}