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Jaworski mock - statements on non-static inner class

sreelakshmi sarma
Ranch Hand

Joined: Mar 02, 2000
Posts: 130
I found this question in Jaworski's mock exam.
Which statement is true about a non-static inner class?
a. It must implement an interface.
b. It is accessible from any other class.
c. It can only be instantiated in the enclosing class.
d. It must be final if it is declared in a method scope.
e. It can access private instance variables in the enclosing object
I answered b&e. But the answer given is only e. Could somebody please explain what am i missing here.
Thanks.
Anonymous
Ranch Hand

Joined: Nov 22, 2008
Posts: 18944
Hi Sree,
If b) was worded more precisely:
"It is DIRECTLY accessible to any other classes"
then you probably wouldn't have selected it.
May be this is what they meant. You probably assumed:
"It is accessible to any other classes, but provided this access is made thru an instance of the outside class".
See JavaRanch good tutorial on this.
JRoch
sreelakshmi sarma
Ranch Hand

Joined: Mar 02, 2000
Posts: 130
Thanks JRoch.
maha anna
Ranch Hand

Joined: Jan 31, 2000
Posts: 1467
Sree,
Even if you have access to the Outer class from Another class you may or may not have access to the inner class in the Another class. To put it simple, If the inner class is private to the outer class then you CANNOT access it from other classes. See the foll example. If I remove the comment a compiler error will occur. You know which error.
<pre>
class Outer {
private class PrivateInner {
}
class PackageInner {
}
void m1() {
PrivateInner privateInner = new PrivateInner();
PackageInner pacakgeInner = new PackageInner();
}
}
class AnotherClass {
void m2() {
Outer outer = new Outer();
//Outer.PrivateInner outerPrivate = outer.new PrivateInner();
Outer.PackageInner outerPaclkage = outer.new PackageInner();
}
}
class test {
static public void main(String[] args) {
}
}
</pre>
Jim Yingst
Wanderer
Sheriff

Joined: Jan 30, 2000
Posts: 18671
Two more things:
A "non-static inner class" could also include a local class or an anonymous class (which is a type of local class). These are not accessible outside their scope. Probably Jaworski meant a non-static member class.
A member class will not be accessible in outside classes unless it has an appropriate access modifier. So B is not true in general unless the class is public.
I'm moving this to Mock Exam Errata. Thanks!

"I'm not back." - Bill Harding, Twister
 
 
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