Worthiness of Java Certification

I have been conducting technical interviews for a software company in Vadodara. While conducting the interviews, I found that there are a lot of experienced Java Programmers, who have got nice scores in the Java Certification exams(SCJP), but do not know the basics. A few of them, when questioned about their certification, simply replied that they just prepared from the Kathy Sierra and Bert Bates book and that is the secret of their good score. Most of them failed to answer questions relating to checked and unchecked exceptions, and had no clue about threads. They had wrong concepts related to the use of synchronized keyword. What is the use of such certification, which can be obtained by just mugging up the question and answers from a book.