How do you instantiat a class with a Class.forName( ) method, if the class's
default constructor requires a parameter?
default constructor requires a parameter?
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Re: Instantiating a Class
"Vijay Singh" <vij_singh@hotm ail.com> wrote in message news:<efq4b.198 2$3B2.908@news-binary.blueyond er.co.uk>...[color=blue]
> How do you instantiat a class with a Class.forName( ) method, if the class's
> default constructor requires a parameter?[/color]
The Class.forName(. ..) method only loads the class and executes any
static initializers there may be. It does not instantiate any objects
of the class (except if a static initializer does that). If you write
Class.forName(" X").newInstance (), however, that will create a new
instance of the class, using the constructor with zero parameters.
You can do the following
You can only use the default constructor however (the one with
no parameters), if you wish to pass in parameters you must
create an init() method (or similar) for the class being created
and then you can call it as:
Class class = Class.forName(" MyClass");
Object object = class.newInstan ce();
MyClass myClass = (MyClass) object;
myClass.init(in t myParameter, MyOtherClasses myParameter2);
Hope this helps,
Daniel Goldman
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Re: Instantiating a Class
D Goldman wrote:[color=blue]
> "Vijay Singh" <vij_singh@hotm ail.com> wrote in message news:<efq4b.198 2$3B2.908@news-binary.blueyond er.co.uk>...
>[color=green]
>>How do you instantiat a class with a Class.forName( ) method, if the class's
>>default constructor requires a parameter?[/color]
>
>
> The Class.forName(. ..) method only loads the class and executes any
> static initializers there may be. It does not instantiate any objects
> of the class (except if a static initializer does that). If you write
> Class.forName(" X").newInstance (), however, that will create a new
> instance of the class, using the constructor with zero parameters.
>
> You can do the following
>
> You can only use the default constructor however (the one with
> no parameters), if you wish to pass in parameters you must
> create an init() method (or similar) for the class being created
> and then you can call it as:
>
> Class class = Class.forName(" MyClass");
> Object object = class.newInstan ce();
> MyClass myClass = (MyClass) object;
> myClass.init(in t myParameter, MyOtherClasses myParameter2);
>
> Hope this helps,
> Daniel Goldman
> http://d-goldman.org[/color]
If your class Foo has a constructor like, say
Foo (int i, String s) {...}
You might use
Class cfoo = Class.forName(" Foo");
Constructor con = cfoo.getConstru ctor(Integer.TY PE, String.class);
Object o = con.newInstance (new Object[]{new Integer(27), "Hi !"});
Foo foo = (Foo)o;
add appropriate exception handling :)
Soren
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