title: JTextField, check field
body: <p>My intent is programming a java applet form, whit connection in a database. 
  when the user compile field, how can check the input while compile and show if exist in a database? </p>
  
  <p>example: 
  Username: myuser. near the jtextfield a label status notify if the test exist in the database. the control need check when the user have finish compile field and not when click on the button. how a control strenght of password.
  its possibile? </p>