Welcome to javaranch Liu.
I highly recommend you
head first java, by Bert Bates and Kathy Sierra, it's an excellent book.
If you want to target certification (
SCJP), then
this is the way to go.
The authors (and us
) are always around here so if you happen to have any questions, erratas, etc., you can post it in the appropriate forum and you'll get an answer pretty quick.
good luck
[ August 21, 2003: Message edited by: Andres Gonzalez ]