added ex E

src/exercicses/ex_e/TestingThreadInterferences.java

@@ -0,0 +1,10 @@
+package exercicses.ex_e;
+
+public class TestingThreadInterferences {
+    public static void main(String[] args) {
+        // shared account object
+        Account account = new Account();
+        (new Thread(new Customer("Damien", account))).start();
+        (new Thread(new Customer("Hélène", account))).start();
+    }
+}