Question

I have a class with several member variables, one of which is a DefaultTableModel. My constructor for the class uses a MySQL ResultSet to populate the DefaultTableModel. I would like to generate an exact copy of the DefaultTableModel and store it as another member variable within my class, so I can edit a copy of the variable within my class while maintaining a copy of the original variable.

Below is an outline of my class.

public class MyClass() {

    int i;
    Boolean b;
    DefaultTableModel model;
    DefaultTableModel model2;

    MyClass(ResultSet myRS) {
        //code to initialize i,b,model;
        //code to clone model and save as model2;
        //code to modify model2;
    }

    public DefaultTableModel getModels(String s) {
        //code that returns model or model2;
    }

}

I have been doing some reading but haven’t figured out how to make an exact copy of a variable within a class. I know I can’t just do model2 = model; since this just copies the references of the variable. I made this mistake and found out that editing model2 would also edit model. Everything I have read about clone makes it seem that it is just used to make a new and identical instance of an entire class. Any advice on how to clone a single variable within a class would be greatly appreciated.

Answer 1

Normally if it was your own TableModel subclass rather than DefaultTableModel you could achive this by making your TableModel implement Clonable and get a copy by calling the clone() method.

As you are working with DefaultTableModel instances, you have to go the other way around and do this:

Instead of creating a single Object[][] or Vector instance for passing data to the constructor of DefaultTableModel, create two copies of Object[][] or Vector. With these you can create both DefaultTableModel instances with the same content.