This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Do you mean that you want to block out the letters that they type, like when you enter a password? In a console you would not get the input from System.in until they pressed enter, so you would NOT get a chance to mess with it at all. Consider a small JOptionPane using the showInputDialog and have the input go into a JPasswordField component.
"JavaRanch, where the deer and the Certified play" - David O'Meara