It costs you about 150 USD. For details, please visit java.sun.com and you will find a link to subjects about certificates. I am a Sun
certified programmer. I don't think a certificate can bring you a job. Of course, getting such a certificate can force you to lay down a solid foundation in Java language.
Please do not rely on the certificates. Companies needs hands-on Java experiences in Java projects. If you have ever done one or two true projects in Java, it will help you a lot in job hunting.