How to handle cancel option in JOptionPane

[Lisa Foster]

When I click cancel on this below option it throws alot of errors how to handle this???
Thanks Lisa

//prompt for server and port number.
serverPort = (String)JOptionPane.showInputDialog(flightTable, "Enter the server and port number of the network database. \n I.E. Server:Port");
serverPort = serverPort.trim();
if (serverPort.equals("") | | serverPort.equals(null)) // user has not entered a server
JOptionPane.showMessageDialog(flightTable,"You have not enter a server and/or port.","Server Error", JOptionPane.ERROR_MESSAGE);
else{ //user entered a server
.
.
.
.
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[Dilip kumar]

seats = JOptionPane.showInputDialog(frame, "Please enter number of tickets :");
// Do nothing if user clicks on Cancel button.
if ( seats == null ) return;
// Handle if user enters 0 or space and clicks OK
if(seats.equals("") | | seats.trim().length()==0 | | Integer.valueOf(seats).intValue()==0) {
JOptionPane.showMessageDialog(null, "Please enter valid number.", "Invaid Entry", JOptionPane.INFORMATION_MESSAGE );
return;
}
Hope this helps.

[Lisa Foster]

Thanks it works fine
Lisa