void createDatabase()
{
em.getTransaction().begin();
Customer alice = createCustomer("Alice", "Switzerland", 100, 200);
Customer bob = createCustomer("Bob", "Switzerland", 200, 300);
Customer carol = createCustomer("Carol", "USA", 300, 250);
Customer dave = createCustomer("Dave", "UK", 100, 500);
Customer eve = createCustomer("Eve", "Canada", 10, 30);
em.persist(alice);
em.persist(bob);
em.persist(carol);
em.persist(dave);
em.persist(eve);