Unknown number of arguments of method in reflection

For example I have a class PartE such:

public class PartE implements Part
{
  protected String method = "getIndex" ;

  protected String getIndex ( double dummy,int dummyInt,String dummyString )
  {
    return "E" ;
  }
}

In this code I should invoke a method with unknown number of arguments. In this case it is getIndex(double,int,String).

It can be in this way:
getIndex()
getIndex(int)
getIndex(boolean,int)
getIndex(int,double,boolean)
So whatever combination of arguments.
I have done this but it seems that I am doing error in params[i].newInstance();

because it returns not proper thing for instantiation. That's why I am taking InstantiationException. I got stuck what can I do?

Class c1 = null;

try {
    c1 = Class.forName( "PartE" );
} catch (ClassNotFoundException ex) {}

Object obj = null;
obj = c1.newInstance();

Method [] methods = c1.getDeclaredMethods();

for(Method m:methods)
  {
      m.setAccessible(true);

      Class<?>[] params = m.getParameterTypes();
      Object[] paramObjects = new Object[params.length];

      for (int i = 0; i < params.length; i++) 
      {
          paramObjects[i] = params[i].newInstance();
      }

      try {
         System.out.println(m.invoke(obj, paramObjects));  
      } catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException ex) {}