jcombobox filter in java – Look and feel independent

Firstly you are creating new model everytime and then invoking show popup from code which leads to flickering etc. We can modify the model itself. Secondly you set the currently entered text as selected item which seems to have selectAll behavior as noted by others. I have modified the code as follows:

public void comboFilter(String enteredText) {
    if (!this.isPopupVisible()) {
        this.showPopup();
    }

    List<String> filterArray= new ArrayList<String>();
    for (int i = 0; i < array.size(); i++) {
        if (array.get(i).toLowerCase().contains(enteredText.toLowerCase())) {
            filterArray.add(array.get(i));
        }
    }
    if (filterArray.size() > 0) {
        DefaultComboBoxModel model = (DefaultComboBoxModel) this.getModel();
        model.removeAllElements();
        for (String s: filterArray)
            model.addElement(s);

        JTextField textfield = (JTextField) this.getEditor().getEditorComponent();
        textfield.setText(enteredText);
    }
}

Hope it works for you.