如何检查JComboBox是否为空？

Question

I am not able to check whether the JComboBox is empty. The below code is not working.

if (t_m_priority.getSelectedItem() != null &&
t_m_priority.getSelectedItem().equals("SELECT")){
        msg = "Triage Time Is Not Entered";
        saveflag = false;
    }

Answer 1

JComboBox#getSelectedItem will return null when no items are selected

You could use something like...

if (t_m_priority.getSelectedItem() != null &&
    t_m_priority.getSelectedItem().equals("SELECT")) {

To first check to see if the anything is selected and then test to see what the selected item actually is...

Answer 2

JComboBox.getItemCount()

If this method returns 0, the component is empty.

if (t_m_priority.getItemCount() == 0) {
   msg = "Triage Time Is Not Entered";
   saveflag = false; 
}

UPDATE: Try this to check if no item is selected in the combo box.

if(t_m_priority.getSelectedItem() == null ) {
     msg = "Triage Time Is Not Entered";
     saveflag = false;  
}

Answer 3

Instead of adding the dummy item "Select" to the combo box, use a custom renderer to display "Select" when no item is actually selected. Then you can just check if the selected index of the combo box is not -1.

Check out Combo Box Prompt for a renderer that implements this functionality for you.