AspectJ - Use reflection to instanciate object of not public class

I am trying to instanciate an object of a non public class in AspectJ.

I have this class:

package ca1.business;

public class Bill {

    int id;
    String idOperator;
    String idClient;

    Bill(int id, String idOperator, String idClient) {
        (...)
    }

    public String toString() {
        (...)
    }

    public boolean equals(Object o) {
        (...)
    }

    public int getId() {
        (...)
    }   
    public String getOperator() {
        (...)
    }
    public String getClient() {
        (...)
    }
}

In the aspects class I wanted to be able to do:

Bill b = new Bill(currInvoice, idOperator, idClient);

The problem is that I get an error:

The constructor Bill(int, String, String) is not visible

So I investigated and tried to use reflection like it's explained in this post.

try {
    Constructor<Bill> cons = Bill.class.getDeclaredConstructor(null);
    cons.setAccessible(true);
    Bill invoice = cons.newInstance(null);
    invoice.id = 1;
    invoice.idOperator = "foo";
    invoice.idClient = "bar";
    // etc...
} catch (SecurityException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (NoSuchMethodException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IllegalArgumentException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (InstantiationException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IllegalAccessException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (InvocationTargetException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

But I get an error in the lines:

invoice.id = 1;
invoice.idOperator = "foo";
invoice.idClient = "bar";

The error is:

The field Bill.X is not visible.

Does anyone know if there is any workaround?