ComboBox problems in java

ComboBox problems in java

Can i do something like after i clicked the button then the combo box
appear,the combo box only appear when i clicked the button.Is it even
possible?
Here is my code:
search.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent ev) {
if(c3.getSelectedItem()=="First Floor"){
p1.add(c42);
}
});
The c3 is another combo box which contain from ground floor to fourth
floor and c42 is combo box which contains room numbers for only First
floor,i need something like when i clicked the search button then the c42
appear.