Trying to implement it so that the text in my JSpinner / JTextField's are selected when it gains focus I implemented this class (modified version of one I found in this forum):

public class CommonUtilityMethods {
    private static FocusAdapter allTextSelector;
    // Ensures that all the text in a JTextComponent will be
    // selected whenever the cursor is in that field (gains focus):
    public static void setSelectAllFieldText(JComponent comp) {
        if (allTextSelector == null) {
            // Lazy initialization of one adapter for all components:
            allTextSelector = new java.awt.event.FocusAdapter() {
                public void focusGained(FocusEvent ev) {
                    if(ev.getSource() instanceof JTextComponent) {
                        JTextComponent textComp = (JTextComponent) ev.getSource();
                        textComp.selectAll();
                    } else if(ev.getSource() instanceof valueSpinner) {
                        valueSpinner vcomp = (valueSpinner)ev.getSource();
                        ((JSpinner.DefaultEditor )vcomp.getEditor ()).getTextField().selectAll();
        comp.addFocusListener(allTextSelector);
}

And then I add the listener using the setSelectAllFieldText method.
It does however not work as expected. On JTextField's a selection is only made the first time the textfield gains focus (so I get it to select all text if I remove the focus from the JInternalFrame which it is located in and then give it focus again).
On JSpinner no selection is made at all..