mixed type collections

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meridian - 15 Mar 2007 15:31 GMT

In Java can you mix types in collections or arrays like in Python and
Ruby?
(eg like the Python and Ruby examples here...)

># Python
> class MyClass:
> def __str__(self):
> return "I'm an object of MyClass"
>
> myObj = MyClass()
>
> l = [0, 1.1, "2", "three", myObj]
>
> for thing in l:
> print thing
>
> # output
> #
> # 0
> # 1.1
> # 2
> # three
> # I'm an object of MyClass

-------------------------------------------

># Ruby
> class MyClass
> def to_s
> return "I'm an object of MyClass"
> end
> end
>
> myObj = MyClass.new
>
> l = [0, 1.1, "2", "three", myObj]
>
> for thing in l
> puts thing
> end
>
> # output
> #
> # 0
> # 1.1
> # 2
> # three
> # I'm an object of MyClass

thanks for your help....

Reply to this Message

Ingo R. Homann - 15 Mar 2007 16:04 GMT

Hi,

I am not aware of the Python and Ruby syntax you posted, but of course
it is possible in Java as well:

Object[] os=new Object[]{"Hello World",new Integer(43)};

Having said this - I think that is not a good idea. The advantage of
Java over other (Script) languages is its strong and static type
information. (*) I suppose, a solution with a common super class (or
interface) would be a better idea. But that can only be decided if we
knew more about your *real* problem.

Ciao,
Ingo

(*) Some people think the opposite: that static type information is an
disadvantage. After all it is only a question of your individual
preference. But if you think that static typing is a disadvatage, then
you should not use Java. It's just that easy.

Reply to this Message

meridian - 15 Mar 2007 16:29 GMT

Thanks Ingo,
It wasn't a real world problem. I'm trying to learn some Java & Ruby
(I normally use python).
So when Ruby's basic examples showed this:
a = [ 3.14159, "pie", 99 ]
a.type » Array
a.length » 3
a[0] » 3.14159
a[1] » "pie"
a[2] » 99
a[3] » nil
I thought, yep I can do that in python but I couldn't in Java.
I can now though... thanks.
Wasn't advocating any preference about typing etc.
Cheers
Steve

Reply to this Message

Wojtek - 15 Mar 2007 16:36 GMT

meridian wrote :

> Thanks Ingo,
> It wasn't a real world problem. I'm trying to learn some Java & Ruby
[quoted text clipped - 10 lines]
> I can now though... thanks.
> Wasn't advocating any preference about typing etc.

Ok, but what you are really doing here is using an array as a container
for properties. In Java you would create a class with these properties
and use get/set to access them.

That way, when you want to pass the container to a method, you get the
compiler to ensure that the right container (object) gets passed in.

In PHP, all you can do is "hope" that the right array was passed in.

If you use an Object array, you are back to hoping that the right
Object array gets passed in.

Signature

Wojtek :-)

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