how can i conside the upper letter and lower letter case when the user use the user id to login.
it is because when the user table have the user id is 'AM'
when the user type lower letter 'am' that i can login to the system.
how can i match the letter that exactly same as the database then let user login.
I suppose that user name is string.
It means that String is an object, not primitive (primitives start with lower case letter - int, boolean etc., classes start with upper case letter - String, Integer etc.)
"==" is used to compare primitive values, not objects.
So check the String api and you'll find out the right way to compare
two strings (of objects) plus other very useful methods that can help you.