Checking if entity exist in Google App Engine Datastore using JPA 1

Question

Below is my method in checking if entity already exist.

public boolean isExist(String genreName) throws PersistenceException{
    EntityManager em = EMF.get().createEntityManager();
    boolean flag = false;

    try{
        Genre genre = em.find(Genre.class, genreName);
        if (genre != null)
            flag = true;

    }finally{
        em.close();
    }

    return flag;
}

Is the code above ok? Please suggest.

Answer 1

• isExist is not English. Call it something like genreExists.
• In addition to omitting the flag, as palacsint suggested, you can get rid of the if branch:

---

public boolean genreExists(String genreName) throws PersistenceException {
    EntityManager em = EMF.get().createEntityManager();
    try {
        return em.find(Genre.class, genreName) != null;
    } finally {
        em.close();
    }
}

---

Probably irrelevant side note:

If you were using Java 7, and EntityManager implemented AutoCloseable or one of its various subinterfaces (such as Closeable), your code could be even cleaner using the new try-with-resources statement:

try (EntityManager em = EMF.get().createEntityManager()) {
    return em.find(Genre.class, genreName) != null;
}

But it doesn't, so you can't.

Answer 2

It looks fine. You could omit the boolean flag if you return immediately when you know the answer:

public boolean isExist(final String genreName) throws PersistenceException {
    final EntityManager em = EMF.get().createEntityManager();
    try {
        final Genre genre = em.find(Genre.class, genreName);
        if (genre != null) {
            return true;
        }
        return false;
    } finally {
        em.close();
    }
}