Thread: instantiation exception

i dont know how to create an instance of an inner class using classloader? here is my code in java.
plz help. emergency question

package a;
public class outer{
public outer(){}
public class inner{
public inner(){}
}

}
------------
package test;
public class main{
static void main(){
//how to create an instance of inner class by classLoader.loadclass??
//i have tried but I face instantiation exception
}
}

Originally Posted by Norm

Can you post more details? What is the name of the classs?
What class and methods are you trying to use to load that class?

tnx for ur reply
i used this code:
public static void main(){
outer o=new outer();
inner i=o.new inner ();
i=(inner)Class.forName("a.outer$inner").newInstanc e();
}

the error was instantiation exception

<code>
package a;


public class A {

public A(){System.out.println("a constructed");}


public class B{

public B(){System.out.println("b constructed");}

}

}


--------------------------------------------
package helloworld;

import a.A;
import a.A.B;


public class Main {


public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {

A a=new A();
B b=a.new B();
b=(B)Class.forName("a.A$B").newInstance();



}

}
</code>
---------------------------------
output is:

a constructed
b constructed
Exception in thread "main" java.lang.InstantiationException: a.A$B
at java.lang.Class.newInstance0(Class.java:340)
at java.lang.Class.newInstance(Class.java:308)
at helloworld.Main.main(Main.java:25)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

--- Update ---

[CODE]

package a;


public class A {

public A(){System.out.println("a constructed");}


public class B{

public B(){System.out.println("b constructed");}

}

}




package helloworld;

import a.A;
import a.A.B;


public class Main {


public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {

A a=new A();
B b=a.new B();
b=(B)Class.forName("a.A$B").newInstance();



}

}

Originally Posted by Norm

Please edit your post and wrap your code with
[code=java]
<YOUR CODE HERE>
[/code]
to get highlighting and preserve formatting.

ok, really Sorry

 
package a;
 
 
public class A {
 
    public A(){System.out.println("a constructed");}
 
 
    public class B{
 
        public B(){System.out.println("b constructed");}
 
    }
 
}
 
 
 
package helloworld;
 
import a.A;
import a.A.B;
 
 
public class Main {
 
 
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
 
     A a=new A();
     B b=a.new B();
     b=(B)Class.forName("a.A$B").newInstance();
 
 
 
 
 
    }
 
}

output:
a constructed
b constructed
Exception in thread "main" java.lang.InstantiationException: a.A$B
at java.lang.Class.newInstance0(Class.java:340)
at java.lang.Class.newInstance(Class.java:308)
at helloworld.Main.main(Main.java:25)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)

Originally Posted by Norm

Have you researched if this is possible?

I have a code that has run before, but now i cant run it. i know there should be a way...

--- Update ---

HooRAY, I found the way

package helloworld;
 
import a.A;
import a.A.B;
 
/**
 *
 * @author alieh
 */
public class Main {
 
 
 
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
 
 
        Class<B> b=null;
        ClassLoader classLoader = ClassLoader.getSystemClassLoader();
        b = ( Class<B> )Class.forName( "a.A$B",false,classLoader);
 
 
 
 
 
 
 
    }
 
}

--- Update ---

Dear Norm,
really tnx for ur attention and reminding me to research;-)