It is actually somewhat rare to actually need a FocusTraversalPolicy because the default tab ordering is the order the components were added to the container.

If that doesn't suit your needs though then you indeed need a FocusTraversalPolicy. It is an abstract class and the abstract methods to override seem to be pretty straightforward, and they have good JavaDoc. Do you have a specific question?

Here is a ridiculous example that may get you going in the right direction. This is a ridiculous example because the same behavior occurs just by adding userNameField to the container before passwordField. However, it does demonstrate how to use it:

public class AuthFormFocusPolicy extends FocusTraversalPolicy {
        private JTextField userNameField;
        private JTextField passwordField;

        public AuthFormFocusPolicy() {
            this.userNameField = new JTextField();
        this.passwordField = new JTextField();
        }

         public Component getInitialComponent(Window window) {
            return super.getInitialComponent(window);
       }

        public Component getDefaultComponent(Container focusCycleRoot) {
            return this.userNameField;
        }

        public Component getComponentAfter(Container focusCycleRoot, Component component) {
            Component nextComponent;
            if (component == this.userNameField) {
            nextComponent = this.passwordField;
            } else {
              nextComponent = this.userNameField;
             }

        return nextComponent;
    }

    public Component getComponentBefore(Container focusCycleRoot, Component component) {
        Component previousComponent;
        if (component == this.userNameField) {
            previousComponent = this.passwordField;
        } else {
            previousComponent = this.userNameField;
        }

        return previousComponent;
    }

    public Component getFirstComponent(Container focusCycleRoot) {
        return this.userNameField;
    }

    public Component getLastComponent(Container focusCycleRoot) {
        return this.passwordField;
    }
}