Consider using the the JPasswordField: How to Use Password Fields (The Java™ Tutorials > Creating a GUI With JFC/Swing > Using Swing Components)
Type: Posts; User: aussiemcgr
Re: JTextField:four digit in the middle displayed as wildcard while user type the number
Consider using the the JPasswordField: How to Use Password Fields (The Java™ Tutorials > Creating a GUI With JFC/Swing > Using Swing Components)