Someone

boolean b = true;

for (int i=0; i < noOfComboBoxes; i++) {
	if(jComboBox[i].getSelectedItem() != "")
	{
		saveMethod();
	}
	else {
		b = false;
 	}
}
                
if(b == false)
{
	OptionPane.showMessageDialog(this, "Complete the missing fields!", "Error", JOptionPane.ERROR_MESSAGE);
}