When a user enters a password, it is preferable that the password is not displayed, so a person peeking over the shoulder of the person at the keyboard can't see the password.
Sun has a mind boggling way to solve this in Java: SPAWN A THREAD THAT QUICKLY SPITS OUT BACKSPACE CHARACTERS!
I really should not shout that much, but... really? That is their solution, really??
Yes, it actually is:Password Masking in the Java Programming Language.
The. Mind. It. Boggles.