meetnaveen4u

 Profile Answers by meetnaveen4u 

• Jul 31st, 2006

 

We can do by the reflection mechanism. For example here is the code.

TestConstructor testConstructor; // This is my class which i want to call.

For arguments of construtor.

Class[] args = new Class[] {String.class} // specify the type of arugument and with no of aruguments.

Declare the value for argument ie. String a1 = "abc";

Object[] argObj = new Object[] {a1}

Get the Construtor object of TestConstructor object i.e

Constructor defaultConstruct = Class.forName("packagename.TestConstructor").getConstructor(args);

TestConstructor test = (TestConstructor) defaultConstruct.newInstance(argObj).

This gives you the class object so u can call repective methods available with the class like test.display();

Hope this answer your question.

Thanks

Naveen.

utpal_utkalit

 Profile Answers by utpal_utkalit Questions by utpal_utkalit

• Nov 16th, 2006

 

try{

System.out.println("class name is "+class_name);

Class cls=Class.forName(class_name);

Constructor[] ctorlist=cls.getConstructors();

/*

*temporary remove the sysout statement

*

*

*/

/*

* to go to the list box

*

*/

for(int i=0;i<ctorlist.length;i++)

System.out.println(ctorlist[i]+"i="+i);

partypes= ctorlist[inx].getParameterTypes();

Constructor ctor= cls.getConstructor(partypes);

argcnt=partypes.length;

System.out.println("argcnt="+argcnt);

arglist= new Object[argcnt];

/*

*call to verify the argument

*/

boolean temp=comparevalidate();

if(objectlist.size()>0)

System.out.println("object list is ::" + objectlist.toString());

for(int i=0;i<arglist.length;i++)

System.out.println("arglist"+arglist[i].toString());

if(temp==true){

System.out.println("created new object");

Object retobj = ctor.newInstance(arglist);

objectlist.add(retobj);

if(objectlist.size()>0)

System.out.println("object list is new::" + objectlist.toString());

/*else

if((argcnt==0) && (paramValues.size()==0))

{

Object retobjnew = cls.newInstance();

objectlist.add(retobjnew);

System.out.println("inside default constructor");

}*/

}

}catch(Exception ex){ex.printStackTrace();}

venkat soma

• Jan 5th, 2007

 

We cant call parameterized constructors by using newInstance() method. Bcoz, newInstance() method will use default constructor to create an object of a class.

Ex:

public class Sample

{

}

if we write

     (Sample)Class.forName("Sample").newInstance();  -- it will return object of type Sample.

bcoz, we didnt provide any constructor. So compiler will add one default constructor. newInstance() method will make use of that default constructor to create object.

suppose if the Sample class is like this --

class Sample

{

     sample(int a){}

}

(Sample)Class.forName("Sample").newInstance() will rise an error. Bcoz, there is no default constructor.