> I need that in a Java program, when I write in its
> Terminal, the things I write don't appear in that
> terminal.
If you have Java 1.6 installed, you can use the readPassword(...) method from the Console class:
http://java.sun.com/javase/6/docs/api/java/io/Console.html
Else, have a look at this article:
http://java.sun.com/developer/technicalArticles/Security/pwordmask/
Good luck.