Passing a parameter through constructor

Question

First I will present a quick outline of a somewhat tightly coupled classes (though not the worst possible case):

class setUpGUI {

   ...
   JTextField output = new JTextField();
   ...
   CountTimer ct;
   ...

   public void setOtputText(String text) {
       output.setText(text);

   public startTimer() {
      ct = new CountTimer();
   }

   ...
}

class CountTimer implements ActionListener {

    private String text = "";
    private gui = new SetUpGUI();
    ...

    @Override
    public void actionPerformed(ActionEvent e) {
        ...
        gui.setOtputText(text);
        ...
    }

My question is about the second snippet (in comparison with the first and on its own):

// functionally equivalent to com.google.gwt.user.client.ui.HasText
interface HasText {

    String getText();
    void setText(String text);

}

class setUpGUI {

   ...
   JTextField output = new JTextField();
   ...
   CountTimer ct;
   ...

   public void setOtputText(String text) {
       output.setText(text);

   public startTimer() {
      ct = new CountTimer(output);
   }

   ...
}

class CountTimer implements ActionListener {

    private String text = "";
    private HasText txtComp;
    ...

    CountTimer(txtComp) {
        ...
        this.txtComp = txtComp;
        ...
    }


    @Override
    public void actionPerformed(ActionEvent e) {
        ...
        txtComp.setText(text);
        ...
    }
}

I believe that the second design can be considered a loose coupling, since instead of using a setter it passes a reference through constructor and at the same time defines its own HasText interface (since Swing does not seem to have one and I didn't find a common parent of JtextComponent and JLabel that has setText() method). Would you agree?

What is the general attitude towards passing a parameter via constructor?

Answer 1

Your second example passes a textual view component to a class that implements ActionListener. Instead, consider a class that extends AbstractAction to allow centralized handling of action events. In the particular case of a text component, TextAction provides access to the focused text component and the underlying Document model to which the JTextComponent listens. As concrete examples, outlined here and here, such pre-defined actions are used throughout the EditorKit hierarchy.

For periodic actions, such as might occur in response to a timer, consider letting the ActionListener update the text component's Document; the listening view will update itself automatically in response. In this case, the listener's constructor would receive a reference to the text component's model.