Creating instance of class within class

Question

Consider that I have the two following nested classes:

public class Foo {

    public class Bar {

    }

}

And my goal is to create an instance of class Bar. I've tried to do it the following ways:

// Method one
Foo fooInstance = new Foo();
Foo.Bar barInstance = new fooInstance.Bar // fooInstance cannot be resolved to a type

// Method two
Foo.Bar barInstance = new Foo.Bar(); // No enclosing instance of type Foo is accessible

Any help would be highly appreciated, I'm stuck. As you might notice, I'm a Java-beginner: which doesn't automatically make this a homework question (as a matter of fact - it isn't).

How can one create an instance of the Bar class? Preferably with the same Foo instance.

Paul Bellora · Accepted Answer · 2012-08-23 20:36:21Z

4

Close. Instead write:

Foo.Bar barInstance = fooInstance.new Bar();

answered Aug 23, 2012 at 20:36

Paul Bellora

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Comments

Razvan · Accepted Answer · 2012-08-23 20:53:01Z

3

Here:

Foo.Bar barInstance = new fooInstance.Bar // fooInstance cannot be resolved to a type

you try to instantiate a type that doesn't exist (fooInstance is just a variable)

The right way to do that is, as explained:

Foo.Bar barInstance = new Foo().new Bar()

Here:

Foo.Bar barInstance = new Foo.Bar(); // No enclosing instance of type Foo is accessible

this is valid only for static inner classes of Foo. So, make Boo a static inner class of Foo if this fits your needs

edited Aug 23, 2012 at 20:53

answered Aug 23, 2012 at 20:41

Razvan

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Comments

Nandkumar Tekale · Accepted Answer · 2012-08-23 20:43:06Z

2

You have to create object of inner class like :

Foo.Bar barObj = new Foo().new Bar();

If inner class is static, then you can create them directly as :

public class Foo {    
    static public class Bar {    
    }    
}

Foo.Bar b = new Foo.Bar();

edited Aug 23, 2012 at 20:43

answered Aug 23, 2012 at 20:37

Nandkumar Tekale

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1 Comment

dnault Over a year ago

+1 for making the inner class static if you can. Instantiating a non-static inner class from outside the containing class may indicate a problem with your design.

kosa · Accepted Answer · 2012-08-23 20:38:14Z

0

It should be

Foo.Bar barInstance = new Foo().new Bar();

answered Aug 23, 2012 at 20:38

kosa

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