Making a Login Prompt | Java | Adding Validation on User Input [ 4/4 ]

disclaimer, last vid omg for login prompt. I guess there will be no part 5 in real soon, so I'll keep it just into 4 series. because of some reasons :/. Btw, this time, we add validation rules so it will prevent any special characters on the input. it can be customize tho :D
.
Text Editor : Sublime 3
OpenJDK : Java 8