Top level class??

[Swapna James]

Hi,

This is a question from a mock exam.

Given the following classes declaration in the same file MyClass1.java

 
package mypackage;
 
public class MyClass1{
//Some Valid Code 
}
 
protected class MyClass2{
//Some Valid Code
}
 
 

A.Two classes can never be declared in the same file.

B.The code Does't compile as the top most class is
protected.

C.The code compiles & MyClass2 can only be instantiated
in it's sub classes.

D.The code compiles & MyClass2 can only be instantiated
by the classes in the package 'mypackage'.

B is the answer. I thought top most class the the one with the widest access modifer.

Can anybody explain to me why MyClass2 is the top level class here and how to identify it?

[Abhishek Jain]

Hi Swapna

Top level classes are those which are not nested in any other class..
Let me explain it to u with an example
Class A{
Class B{
}
}
Class C{
}

if code is like this then
A: Top Level Class
B: Not a Top level class <==
C: Top Level Class

and haa
Top level classes can only be public or default
else the code will not compile

I think u can understand the meaning

Regards
Abhishek

[A Kumar]

Am not sure myself how the protected class is topmost class..


but u cannot have a class with specifier protected....

only public final static

Regards

[Swapna James]

Thanks Abhi,

The explanation is very clear. I got the concept.

Swapna.

[Jim Yingst]

The given answer B is nonsense. If you've transcribed it correctly, then evidently this mock exam was written by an unreliable author. Do not spend time worryng about what the author is telling you - it's wrong; the author was confused.

A top-level class is a class that is not nested in any way. In the code shown, there are two top-level classes, MyClass1 and MyClass2. These are considered top-level, regardless of the access modifier.

You may encounter discussion of "top-level nested classes" or "static inner classes", which used to be considered top-level. This information is old (from before 2001), and should be ignored if you hear it now, as it will be unnecessarily confusing. Top-level classes are not nested. Period.

The correct answer would be that the code does not compile because, if there is more than one top-level class in a file, only one may be public, and the rest must be package access (no access modifier).

[Swapna James]

Thanks Jim,

Before the error was

  
MyClass1.java:7: modifier protected not allowed here
protected class MyClass2{
          ^
1 error

Now that I changed the protected modifier the class is compling.
Swapna