Is any class is an array?

[Hanadi Al-Naimi]

Hi..
I am studying the SCJP exam from Osborne book (Java2- Sun Certified Programmer & Developer for Java2), and I did not understand this idea. I wish I can find any help here.

The instanceof comparison:
With this example:
interface Face{ }
class Bar implements Face { }
class Foo extends Bar {}

The book is saying when we compare this: ( Foo[] instanceof Foo or Bar, or Face) the answer will be false. How we can set the class as an array???

[Steven Bell]

That is because Foo[] is instanceof Array.
Foo[index] would be instanceof Foo ect.

maybe this is a better example:

Foo fooInstance = new Foo();  //create a Foo instance
Foo[] fooArray = new Foo[10]; //an Array of type Foo
fooArray[0] = fooInstance;    //store the Foo instance in the array
 
fooInstance instanceof Foo //true, also Bar and Face
fooArray instanceof Foo    //false
fooArray instanceof Array  //true
fooArray[0] instance of Foo//true, also Bar and Face

when you create and Array, new Foo[10], you do not create any Foo objects you create an Array object that hold type Foo and has a length of 10.

[meena latha]

ok Bell
If v remove

fooArray[0] = fooInstance;

then
fooArray[0] instance of Foo; //false

i am write.

[osman cinar eren]

Actually the question should be wrong:

the compared object`s and the class type must be on the same class hierarchy. so
Foo[] instanceof Foo

gives a COMPILER ERROR.

[Steven Bell]

Originally posted by Ramya JP:
ok Bell
If v remove

fooArray[0] = fooInstance;

then
fooArray[0] instance of Foo; //false

i am write.

yes, because fooArray[0] == null.