Inner classes

[Shubh Bhat]

[
class Outer {
static class Inner {
public Inner()
{
}
}
}
class InheritInner extends Outer.Inner {
public static void main(String [] args) {
Outer o = new Outer();
o.new Inner(); //1
Inner base = new Inner(); // 2
InheritInner ii = new InheritInner();
}

}
]
Why can't I do something like //2 ?
Why do I need an instance of Outer class to instantiate Inner class like in //1

[Barkat Mardhani]

Hi Shubh:
You do not have to create an outer class object to create an instance of static inner class. It is matter of name visibility:

class Outer { 
static class Inner {
public Inner() { } 
static class InnerInner {
public InnerInner() {}
}
}
}
class InheritInner { 
public static void main(String [] args) { 
Outer.Inner base = new Outer.Inner(); // 2 
                Outer.Inner.InnerInner ii = new Outer.Inner.InnerInner();
}
}

However if InheritInner extends Outer, then all members (except private) are implicity known by simple name in InheritInner. See code:

class Outer { 
static class Inner {
public Inner() { } 
static class InnerInner {
public InnerInner() {}
}
}
}
class InheritInner extends Outer { 
public static void main(String [] args) { 
Inner base = new Inner(); // 2 
Inner.InnerInner ii = new Inner.InnerInner();
}
}

Another variation:

class Outer { 
static class Inner {
public Inner() { } 
static class InnerInner {
public InnerInner() {}
}
}
}
class InheritInner extends Outer.Inner { 
public static void main(String [] args) { 
Outer.Inner base = new Outer.Inner(); // 2 
InnerInner ii = new InnerInner();
}
}

You can also play with import statement to change the visibility of class or inner class...
Hope this helps
Barkat
[ September 20, 2002: Message edited by: Barkat Mardhani ]
[ September 20, 2002: Message edited by: Barkat Mardhani ]

[Shubh Bhat]

I really don't understand much I think I am confused as to what happens when an inner class in inherited. If there is a documentation please let me know. I would love to read.
Or can anyone please explain different scenarios of what happens when I extend an inner class. Also, whats up with super(). I mean why can I do o.super in the example I gave above.
Really very confused.

[Jose Botella]

Why can't I do something like //2 ?

Inner class doesn't exist. The name is Outer.Inner, thus the name of the constructor really is Outer.Inner

Why do I need an instance of Outer class to instantiate Inner class like in //1

This doesn't compile in JSDK 1.4

[Barkat Mardhani]

Hi Jose:

quote:
--------------------------------------------------------------------------------
Why do I need an instance of Outer class to instantiate Inner class like in //1
--------------------------------------------------------------------------------

This doesn't compile in JSDK 1.4

Jose, I am not following your point. I contend that you do not need an outer class object to create an instance of STATIC inner class. Only issue is name visibility of STATIC inner class at the point you want to create that object....