how to create object by getting class name as input
hi
i need to create object for the existing classes by getting class name as input from the user at run time.
how can i do it.
for exapmle ExpnEvaluation is a class, i will get this class name as input and store it in a string
String classname = "ExpnEvaluation";
now how can i create object for the class ExpnEvaluation by using the string classname in which the class name is storted
Thanks in advance
[448 byte] By [
azhara] at [2007-11-27 5:45:03]
String classname = "ExpnEvaluation";
Object obj = Class.forName(classname).newInstance();
then you need to cast your new obj to the type you want;
note that you have to write the full package path class name, and your class must be in your class path.
Good Luck
Ahmad Elsafty
String classname = "ExpnEvaluation";
Object obj = Class.forName(classname).newInstance();
using this caode i can able to create object but how can i call the methods of the class "ExpnEvaluation" using this object.
i think we have to cast it, can u help me how to cast the obj to the classname that i get as input
azhara at 2007-7-12 15:26:21 >
String classname = "ExpnEvaluation";
Object obj = Class.forName(classname).newInstance();
using this caode i can able to create object but how can i call the methods of the class "ExpnEvaluation" using this object.
i think we have to cast it, can u help me how to cast the obj to the classname that i get as input
azhara at 2007-7-12 15:26:21 >
> i think we have to cast it, can u help me how to cast> the obj to the classname that i get as input... or use the reflection API. See package java.lang.reflect
u can make custome ClassLoader to Trace the Classes in your project
eaajea at 2007-7-12 15:26:21 >
> i think we have to cast it, can u help me how to cast
> the obj to the classname that i get as input
That's exactly the point why you shouldn't be doing this. You can't have a dynamic cast at compile time already. It doesn't make sense. Which is also the reason why class.forName().newInstance() is a very nice but also often very useless tool, unless the classes loaded all share a mutual interface.
That's exactly the point why you shouldn't be doing this. You can't have a dynamic cast at compile time already. It doesn't make sense. Which is also the reason why class.forName().newInstance() is a very nice but also often very useless tool, unless the classes loaded all share a mutual interface.
then what can i do do create object by getting class name as input
azhara at 2007-7-12 15:26:22 >
use Reflection
eaajea at 2007-7-12 15:26:22 >
> then what can i do do create object by getting class
> name as input
Find a way to do it by doing something different. Like a Hashmap full of functor instances that all have a Runner interface with a runMe() method, for example. I can't tell you what to do since I don't know your requirements.
Here's an example (not tested):
Object o = Class.forName(yourClassName).newInstance();
Method m = o.getClass().getMethod(yourMethodName, new Object[] {/* your parameter types */});
Object result = m.invoke(o, new Object[] {/* your parameters */});
> use ReflectionWhich of course means keeping meta-data for each class: name, and which method to call after instantiating it, and what the arguments and return values might be... which you then still can't handle. :p
> Here's an example (not tested):
> > Object o =
> Class.forName(yourClassName).newInstance();
> Method m = o.getClass().getMethod(yourMethodName, new
> Object[] {/* your parameter types */});
> Object result = m.invoke(o, new Object[] {/* your
> parameters */});
>
Close. getMethod takes an array of Classes :-)
> Close. getMethod takes an array of Classes :-)My inmind-compiler uses a more tolerant type-check and magical auto-casts ;)
> > Close. getMethod takes an array of Classes :-)> > My inmind-compiler uses a more tolerant type-check> and magical auto-casts ;)Nice. Plzzzzz where to downloads inmindcompiler dynamically, I have doubt plzzzz thankyou sir
> Nice. Plzzzzz where to downloads inmindcompiler> dynamically, I have doubt plzzzz thankyou sirI'm sorry, but your locale is not supported yet. Please register the newsletter from vaporware.biz in order to get all the latest news about our development progress.
> > Nice. Plzzzzz where to downloads inmindcompiler
> > dynamically, I have doubt plzzzz thankyou sir
>
> I'm sorry, but your locale is not supported yet.
> Please register the newsletter from vaporware.biz in
> order to get all the latest news about our
> development progress.
Thankyou dear but I need code samples and explnatin urgently plzzzzzzz
> Thankyou dear but I need code samples and explnatin urgently plzzzzzzz
Sorry gentleman, I didn't know it was ugrent. Here you go:
Result res = null;
try {
res = InmindCompiler.newInstance().compile(/* your stuff here */);
}
catch (BlownUpException ex) {
/* never mind, happens once in a while */
}
catch (SleepModeException ex) {
/* ignore; state should be polled in a loop or use timer to notify */
}
catch (Exception ex) {
res = new PerfectResult(/* your stuff here */, PerfectResult.MAGIC_ON);
}
/* done */
