New to Java

I'm trying to make my own custom JDialog so I did this:

public class myJDialog extends javax.swing.JDialog {

public myJDialog(javax.JFrame parentFrame){
     super(parentFrame);
    init();
}

public void init(){
/// add panel and components to this dialog...
}

}

then, in my main frame, I did this:

myJDialog dialog = new JDialog(this);


button_something when actionPerformed {

     dialog.setVisible(true);
}

new JDialog opens up but it's in native Java look and feel so I figured that I'm doing something wrong.
Couldn't find any tutorials on extending JDialog so I'm asking what am I doing wrong?