[hardwired]

Save a reference to them that you can use later to refer to them.

class Pseudo {
    JTextField textField;
    JButton button = new JButton("hi");

    private void buildUI() {
        testField = new JTextField(12);
        JPanel panel = new JPanel(someLayout);
        panel.add(textField);
        panel.add(button);
    }
}

Or you can use the Container methods like getComponents to access them.

Component[] c = panel.getComponents();
for(int i = 0; i < c.length; i++) {
    System.out.println(c[i].getClass().getSimpleName());
}