How do I pass parameter when using newInstance

[Tony Johansson]

Hello!

I use method forName and newInstance in class Class like this
instance = (GameFactory)(C lass.forName(na me).newInstance () );

Now to my question:
Assume that name is GameFactory then I want to pass a parameter to the
GameFactory constructor
like this instance = (GameFactory)(C lass.forName(na me).newInstance (field) );
Here I pass parameter field which is an int but when I do so I get compile
error saying

F:\gameLab\Game Factory.java(15 ): Cannot find method 'newInstance(in t)' in
'java.lang.Clas s'

How you any idea?

Or is it so that if I want to pass parameter I have to explicitly use new
GameFactory(fie ld);

//Tony

[Oliver Wong]

Re: How do I pass parameter when using newInstance


"Tony Johansson" <johansson.ande rsson@telia.com > wrote in message
news:Ldq5f.1486 27$dP1.506466@n ewsc.telia.net. ..[color=blue]
> Hello!
>
> I use method forName and newInstance in class Class like this
> instance = (GameFactory)(C lass.forName(na me).newInstance () );
>
> Now to my question:
> Assume that name is GameFactory then I want to pass a parameter to the
> GameFactory constructor
> like this instance =
> (GameFactory)(C lass.forName(na me).newInstance (field) );
> Here I pass parameter field which is an int but when I do so I get compile
> error saying
>
> F:\gameLab\Game Factory.java(15 ): Cannot find method 'newInstance(in t)' in
> 'java.lang.Clas s'
>
> How you any idea?
>
> Or is it so that if I want to pass parameter I have to explicitly use new
> GameFactory(fie ld);[/color]

In short, you can't do this. From the JavaDocs:

<quote>
Creates a new instance of the class represented by this Class object. The
class is instantiated as if by a new expression with an empty argument list.
</quote>

- Oliver

[Ian Shef]

Re: How do I pass parameter when using newInstance

"Tony Johansson" <johansson.ande rsson@telia.com > wrote in
news:Ldq5f.1486 27$dP1.506466@n ewsc.telia.net:
[color=blue]
> Hello!
>
> I use method forName and newInstance in class Class like this
> instance = (GameFactory)(C lass.forName(na me).newInstance () );
>
> Now to my question:
> Assume that name is GameFactory then I want to pass a parameter to the
> GameFactory constructor
> like this instance =
> (GameFactory)(C lass.forName(na me).newInstance (field) ); Here I pass
> parameter field which is an int but when I do so I get compile error
> saying
>
> F:\gameLab\Game Factory.java(15 ): Cannot find method 'newInstance(in t)'
> in 'java.lang.Clas s'
>[/color]
<snip>

I don't think that you can do this with Class, but you can use the reflection
package java.lang.refle ct . Use Class.getConstr uctor or
Class.getConstr uctors to get an appropriate Constructor. Then use
Constructor.new Instance to create and initialize an instance.

It is going to be more complex than the no-argument constructor that you were
using before.

Good Luck!


--
Ian Shef 805/F6 * These are my personal opinions
Raytheon Company * and not those of my employer.
PO Box 11337 *
Tucson, AZ 85734-1337 *