How do I pass parameter when using newInstance

[Tony Johansson]

Hello!

I use method forName and newInstance in class Class like this
instance = (GameFactory)(Class.forName(name).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)(Class.forName(name).newInstance(fiel d) );
Here I pass parameter field which is an int but when I do so I get compile
error saying

F:\gameLab\GameFactory.java(15): Cannot find method 'newInstance(int)' in
'java.lang.Class'

How you any idea?

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

//Tony

[Oliver Wong]

"Tony Johansson" <jo*****************@telia.com> wrote in message
news:Ld*********************@newsc.telia.net...

Hello!

I use method forName and newInstance in class Class like this
instance = (GameFactory)(Class.forName(name).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)(Class.forName(name).newInstance(fiel d) );
Here I pass parameter field which is an int but when I do so I get compile
error saying

F:\gameLab\GameFactory.java(15): Cannot find method 'newInstance(int)' in
'java.lang.Class'

How you any idea?

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

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]

"Tony Johansson" <jo*****************@telia.com> wrote in
news:Ld*********************@newsc.telia.net:

Hello!

I use method forName and newInstance in class Class like this
instance = (GameFactory)(Class.forName(name).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)(Class.forName(name).newInstance(fiel d) ); Here I pass
parameter field which is an int but when I do so I get compile error
saying

F:\gameLab\GameFactory.java(15): Cannot find method 'newInstance(int)'
in 'java.lang.Class'

<snip>

I don't think that you can do this with Class, but you can use the reflection
package java.lang.reflect . Use Class.getConstructor or
Class.getConstructors to get an appropriate Constructor. Then use
Constructor.newInstance 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 *