Dao.java

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.Query;

public enum Dao {
    INSTANCE;

    @SuppressWarnings("unchecked")
    public List<Todo> listTodos() {

        EntityManager em = EMFService.get().createEntityManager();
        Query q = em.createQuery("select m from Todo m");
        List<Todo> todos = q.getResultList();
        return todos;
    }

    public void add(String userID, String summery, String description, String url) {

        synchronized(this) {

            EntityManager em = EMFService.get().createEntityManager();
            Todo todo = new Todo( userID, summery, description, url );
            em.persist(todo);
            em.close();

        }
    }

    @SuppressWarnings("unchecked")
    public List<Todo> getTodo(String userID) {

        List<Todo> todos;
        try
        {
            EntityManager em = EMFService.get().createEntityManager(); // Error links to here
            Query q = em.createQuery("select t from Todo t where t.author = :userID");
            q.setParameter("userID", userID);
            todos = q.getResultList();

            return todos;

        }catch(Exception e ){
            System.out.println("This is my error here");
            e.printStackTrace();
        }

        return null;

    }

    public void remove(long id) {

        EntityManager em = EMFService.get().createEntityManager();

        try {
            Todo todo = em.find(Todo.class, id);
            em.remove(todo);
        } finally {
            em.close();
        }
    }
}