选择JCombobox时GUI冻结，如何在ActionListener中使用条件语句在Swing应用程序中使用Timer？

I am working on a login frame where i am retrieving and populating JComboBox with user created databases and then I am setting Text of JLabel on the basis of Item selected from JComboBox. I want to delay the execution and display the 'Connecting...' text in JLabel when user selects an item from JComboBox but when I select an item the GUI freezes and after 5 seconds it shows 'Connected' It skips the 'Connecting...' JLabel.I am working on a login frame where i am retrie