Questions concerning Nested Classes

Question

Hi!
Just read some articles about nested classes (include the ones from the Java Tutorial and the Effective Java chapter), and while most of it is perfectly clear, three questions remain:
1.) When I declare a member class, how should I declare the access specifiers (private, protected etc.) for the member class's attributes and methods? If I declare a member class as private, anything but private for the attributes and methods wouldn't make sense, would it?
2.) The Java Tutorial says:
Also, because an inner class is associated with an instance, it cannot define any static members itself.While this is true for static methods, it seems to be possible to declare static variables inside inner classes. This is confusing me... does it actually make sense to declare static variables inside inner classes (or member classes in general)? Or should the be placed in the declaring class?
3.) Another confusing quote from the Java Tutorial:
Static nested classes do not have access to other members of the enclosing class.This is true for instance variables and methods but not for static variables, which are also members of the enclosing class, aren't they?
Thanks in advance,
OIiver

Answer 1

Trollhorn wrote:
Hi!
Just read some articles about nested classes (include the ones from the Java Tutorial and the Effective Java chapter), and while most of it is perfectly clear, three questions remain:
1.) When I declare a member class, how should I declare the access specifiers (private, protected etc.) for the member class's attributes and methods? If I declare a member class as private, anything but private for the attributes and methods wouldn't make sense, would it?
    private static class MyInner implements Runnable
        @Override public void run() // Must be public!
2.) The Java Tutorial says:
Also, because an inner class is associated with an instance, it cannot define any static members itself.While this is true for static methods, it seems to be possible to declare static variables inside inner classes. This is confusing me... does it actually make sense to declare static variables inside inner classes (or member classes in general)? Or should the be placed in the declaring class?Wrong. It can define static final member variables and I see no reason to move them to the outer class, if they are used only by the inner class.
3.) Another confusing quote from the Java Tutorial:
Static nested classes do not have access to other members of the enclosing class.This is true for instance variables and methods but not for static variables, which are also members of the enclosing class, aren't they?I agree with you here.
Edited by: baftos on Jun 6, 2009 9:18 AM