Dynamically find the correct method in order to not repeat the same code

Question

The following code adds Listeners to several SWT Text elements. The only difference is the code inside the Listeners method. Is there a way to make this code less repetitive by finding the correct method to use dynamically?

In this example a FocusListener is used, but it's not relevant.

private void addFocusLostListeners() {
    nameText.addFocusListener(new FocusListener() {
        @Override
        public void focusGained(FocusEvent e) {}
        @Override
        public void focusLost(FocusEvent e) {
            myDataObject.setName(nameText.getText());
        }
    });
    ageText.addFocusListener(new FocusListener() {
        @Override
        public void focusGained(FocusEvent e) {}
        @Override
        public void focusLost(FocusEvent e) {
            myDataObject.setAge(ageText.getText());
        }
    });
    emailText.addFocusListener(new FocusListener() {
        @Override
        public void focusGained(FocusEvent e) {}
        @Override
        public void focusLost(FocusEvent e) {
            myDataObject.setEmail(emailText.getText());
        }
    });
    ...
}

first of all use `FocusAdapter` and you won't need to override unused methods ... — Adrian, May 15 '19 at 09:54
you don't use `focusGained` from `FocusListener` interface. For such cases in AWT we have adapters, so instead of `new FocusListener()` use `new FocusAdapter()` and override just `focusLost` method — Adrian, May 15 '19 at 10:57

score 4 · Accepted Answer · answered May 15 '19 at 09:56

You could make a helper method (you need to replace TextField with the actual class of nameText, ageText, etc.):

private static void addFocusListener(TextField field, Consumer<? super String> setter) {
    field.addFocusListener(new FocusListener() {
        @Override
        public void focusGained(FocusEvent e) {}
        @Override
        public void focusLost(FocusEvent e) {
            setter.accept(field.getText());
        }
    });
}

Which you then could call:

private void addFocusLostListeners() {
    addFocusListener(nameText, myDataObject::setName);
    addFocusListener(ageText, myDataObject::setAge);
    addFocusListener(emailText, myDataObject::setEmail);
}

but what if myDataObject is null when calling addFocusLostListeners()? — Sadık, May 15 '19 at 10:43
@Sadik just replace the method references (e.g. `myDataObject::setName`) with a lambda (e.g. `s -> myDataObject.setName(s)`) this should solve the problem — Lino, May 15 '19 at 10:46

Dynamically find the correct method in order to not repeat the same code

1 Answers1