如何使用PostgreSQL将登录凭证与数据库JDBC进行比较

So I am attempting to make a simple chat messenger in Eclipse. At the moment I am stumped on how to compare the users login details against those stored in a database table. I have an 'askName()' method that takes a username and password, and this needs to use my 'authenticate' method to check details stored in a Login table in the database.So I am attempting to make a simple chat messen