keep open JComboBox drop-down list

Cell renderer and font problem is solved by calling
JComboBox#setFont() method from within the
renderer mothod. Thanks again all the people who
gave the hint.

Now, I'd like to keep open the drop-down list of the
combo box when a specific kind of items are selected.
However, calling showPopup() and/or
setPopupVisible(true) from the ActionListener method
doesn't do the job. What else should I have done?

TIA, again.

.

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