Accessing inner class from static outer util function

Question

I have a class structure roughly like this:

final public class Util { private Util() { throw new AssertionError(); // there is not supposed to exist an instance } public static DataElem getData() { return new Util().new DataElem(); } public class DataElem { // class definition } }

The code for correctly generating an instance of the inner class was taken from this thread. But I didn't like that every time an inner class instance gets made, an instance from the outer one gets made first. And since I put the AssertionError into its constructor, it doesn't work.

Do I have to carry a dummy-instance around just to create instances from the inner class? Can't I make something like Util.DataElem work?

Add static to the class header for DataElem?

awksp
– awksp

2014-07-09 18:32:36 +00:00
Commented Jul 9, 2014 at 18:32 — awksp
– awksp, Commented Jul 9, 2014 at 18:32

Jigar Joshi · Accepted Answer · 2014-07-09 18:39:08Z

3

You can make your inner class static

final public class Util { private Util() { throw new AssertionError(); // there is not supposed to exist an instance } public static DataElem getData() { return new Util.DataElem(); } private static class DataElem { private DataElem(){} // keep private if you just want elements to be created via Factory method // class definition } }

and then initialize it like

new Util.DataElem();

edited Jul 9, 2014 at 18:39

answered Jul 9, 2014 at 18:33

Jigar Joshi

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9 Comments

Braj Over a year ago

what about this return new DateElem()

Jigar Joshi Over a year ago

@Braj yes what about it ?

Jashaszun Over a year ago

You should remove the = in return = new Util().new DataElem();.

Braj Over a year ago

Simply return new DateElem() there is no need to add the Util class name because it's already inside the Util class.

Jashaszun Over a year ago

@JigarJoshi ... no it wasn't. The = is still an error.

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