Java Application/Class Design - How do accessors in Java work?
How do I write the getDB() function and use it properly?
Here is a code snippet of my App Object:
public class MyApp extends UiApplication {
private static PersistentObject m_oStore;
private static MyBigObjectOfStorage m_oDB;
static {
store = PersistentStore.getPersistentObject(0xa1a569278238dad2L);
}
public static void main(String[] args) {
MyApp theApp = new MyApp();
theApp.enterEventDispatcher();
}
public MyApp() {
pushScreen(new MyMainScreen());
}
// Is this correct? Will it return a copy of m_oDB or a reference of m_oDB?
public MyBigObjectOfStorage getDB() {
return m_oDB; // returns a reference
}
}
Asked by: Rebecca312 | Posted: 23-01-2022
Answer 1
public MyBigObjectOfStorage getDB() {
return m_oDB;
}
As you put it is correct. It will return a copy of the reference, which is kind of in between a copy and a reference.
The actual object instance returned by getDB() is the same object referenced by m_oDB. However, you can't change the reference returned by getDB() to point at a different object and have it actually cause the local private m_oDB to point at the new object. m_oDB will still point at the object it was already.
See http://www.javaworld.com/javaworld/javaqa/2000-05/03-qa-0526-pass.html for more detail.
Although looking through your code there, you never set m_oDB at all, so getDB() will always return null.
Answered by: Hailey806 | Posted: 24-02-2022Answer 2
public MyBigObjectOfStorage getDB() {
Object o = store.getContents();
if ( o instanceof MyBigObjectOfStorage ) {
return (MyBigObjectOfStorage) o;
} else {
return null;
}
}
Answer 3
I am one of those folks that are very much against using singletons and/or statics as it tends to make unit testing impossible. As this is posted under best practices, I suggest that you take a look at using a dependency injection framework. Personally I am using and prefer Google Guice.
Answered by: Kate226 | Posted: 24-02-2022Similar questions
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